Scientific American Supplement, No. 458, October 11, 1884
by
Various
Part 1 out of 3
Produced by by Don Kretz, Juliet Sutherland, Charles Franks and the
DP Team
[Illustration]
Scientific American Supplement No. 458
NEW YORK, OCTOBER 11, 1884
Scientific American Supplement. Vol. XVIII, No. 458.
Scientific American established 1845
Scientific American Supplement, $5 a year.
Scientific American and Supplement, $7 a year.
TABLE OF CONTENTS.
I. CHEMISTRY AND METALLURGY.--Chemical Nature of Starch
Grains.
The Amalgamation of Silver Ores.--Description of the Francke
tina, or vat process for amalgamation of silver ores.--By E.P.
RATHBONE.--6 figures.
Interesting Facts about Platinum.--Draw stones used for drawing
wire of precious metals.
II. ENGINEERING, MINING, ETC.--Modern Locomotive Practice.--Paper
read before the Civil and Mechanical Engineers' Society.--By
H. MICHELL WHITLEY--10 figures.
New Screw Steam Collier, Frostburg.--1 figure.
Destruction of the Tardes Viaduct by Wind.--With engraving.
Joy's Reversing and Expansion Valve Gear.--1 figure.
The Steam Bell for Locomotives.--2 figures.
Diamond Mining in Brazil.--With engravings showing the dam
on the Ribeirao Inferno at Portao de Ferro, and the arrangement
of the machinery.
III. ELECTRICITY, ETC.--The Frankfort and Offenbach Electric
Railway.--With 3 engravings.
Possibilities of the Telephone.--Its use by vessels at sea.
Pyrometers.--The inventions of Siemens and others.
IV. ARCHAEOLOGY.--The Cay Monument at Uxmal.--Discovered by
Dr. Le Plongeon on June 1, 1881.--With engraving.
V. ASTRONOMY.--The Temperature of the Solar Surface Corresponding
with the Temperature Transmitted to the Sun Motor.--By
J. ERICSSON.--With 2 engravings of the sun motor.
VI. HORTICULTURE.--Halesia Hispida, a Hardy Shrub.--With engraving.
Windflowers or Anemone.--With engraving.
VII. MEDICINE, HYGIENE. ETC.--What we Really Know about
Asiatic Cholera.--By J.C. PETERS, M.D.
Dr. Koch on the Cholera.
Malaria.--The natural production of malaria and the means of
making malarial countries healthier.--By C.T. CRUDELI, of Rome.
Story of Lieut. Greely's Recovery.--Treatment by Surgeon
Green.
VIII. MISCELLANEOUS.--Bayle's New Lamp Chimney.--With engraving.
Lieut. Greely before the British Association.
* * * * *
THE FRANKFORT AND OFFENBACH ELECTRIC RAILWAY.
The electric railway recently set in operation between Frankfort and
Offenbach furnishes an occasion for studying the question of such roads
anew and from a practical standpoint. For elevated railways Messrs.
Siemens and Halske a long time ago chose rails as current conductors. The
electric railway from Berlin to Lichterfelde and the one at Vienna are in
reality only elevated roads established upon the surface.
Although it is possible to insulate the rails in a satisfactory manner in
the case of an elevated road, the conditions of insulation are not very
favorable where the railway is to be constructed on a level with the
surface. In this case it becomes necessary to dispense with the simple and
cheap arrangement of rails as conductors, and to set up, instead, a number
of poles to support the electric conductors. It is from these latter that
certain devices of peculiar construction take up the current. The simplest
arrangement to be adopted under these circumstances would evidently be to
stretch a wire upon which a traveler would slide--this last named piece
being connected with the locomotive by means of a flexible cord. This
general idea, moreover, has been put in practice by several constructors.
In the Messrs. Siemens Bros.' electric railway that figured at Paris in
1881 the arrangement adopted for taking up the current consisted of two
split tubes from which were suspended two small contact carriages that
communicated with the electric car through the intermedium of flexible
cables. This is the mode of construction that Messrs. Siemens and Halske
have adopted in the railway from Frankfort to Offenbach. While the Paris
road was of an entirely temporary character, that of Frankfort has been
built according to extremely well studied plans, and after much light
having been thrown upon the question of electric traction by three years
of new experiments.
Fig. 1 shows the electric car at the moment of its start from Frankfort,
Fig. 2 shows the arrangement of a turnout, and Fig. 3 gives a general plan
of the electric works.
[Illustration: FIG. 1.--THE ELECTRIC RAILWAY, FRANKFORT, GERMANY.]
The two grooved tubes are suspended from insulators fixed upon external
cast iron supports. As for the conductors, which have their resting points
upon ordinary insulators mounted at the top of the same supports, these
are cables composed of copper and steel. They serve both for leading the
current and carrying the tubes. The same arrangement was used by Messrs.
Siemens and Halske at Vienna in 1883.
The motors, which are of 240 H.P., consist of two coupled steam engines of
the Collmann system. The one shaft in common runs with a velocity of 60
revolutions per minute. Its motion is transmitted by means of ten hempen
cables, 3.5 cm. in diameter. The flywheel, which is 4 m. in diameter,
serves at the same time as a driving pulley. As the pulley mounted upon
the transmitting shaft is only one meter in diameter, it follows that the
shafting has a velocity of 240 revolutions per minute. The steam
generators are of the Ten Brink type, and are seven in number. The normal
pressure in them is four atmospheres. There are at present four
dynamo-electric machines, but sufficient room was provided for four more.
The shafts of the dynamos have a velocity of 600 revolutions per minute.
The pulleys are 60 cm. in diameter, and the width of the driving belts is
18 cm. The dynamos are mounted upon rails so as to permit the tension of
the belting to be regulated when necessity requires it. This arrangement,
which possesses great advantages, had already been adopted in many other
installations.
The electric machines are 2 meters in height. The diameter of the rings is
about 45 cm. and their length is 70 cm. The electric tension of the
dynamos measures 600 volts.
[Illustration: FIG. 2.--TURNOUT TRACK OF THE ELECTRIC RAILWAY, FRANKFORT,
GERMANY.]
The duty varies between 80 and 50 per cent., according to the arrangement
of the cars. The total length of the road is 6,655 meters. Usually, there
are four cars _en route_, and two dynamos serve to create the current.
When the cars are coupled in pairs, three dynamos are used--one of the
machines being always held in reserve. All the dynamos are grouped for
quantity.
[Illustration: FIG. 3.--GENERAL PLAN OF THE ELECTRIC WORKS.]
The company at present owns six closed and five open cars. In the former
there is room for twenty-two persons. The weight of these cars varies
between 3,500 and 4,000 kilos.--_La Lumiere Electrique._
* * * * *
By the addition of ten parts of collodion to fifteen of creasote (says the
_Revue de Therap._) a sort of jelly is obtained which is more convenient
to apply to decayed teeth than is creasote in its liquid form.
* * * * *
POSSIBILITIES OF THE TELEPHONE.
The meeting of the American Association was one of unusual interest and
importance to the members of Section B. This is to be attributed not only
to the unusually large attendance of American physicists, but also to the
presence of a number of distinguished members of the British Association,
who have contributed to the success of the meetings not only by presenting
papers, but by entering freely into the discussions. In particular the
section was fortunate in having the presence of Sir William Thomson, to
whom more than to any one else we owe the successful operation of the
great ocean cables, and who stands with Helmholtz first among living
physicists. Whenever he entered any of the discussions, all were benefited
by the clearness and suggestiveness of his remarks.
Professor A. Graham Bell, the inventor of the telephone, read a paper
giving a possible method of communication between ships at sea. The simple
experiment that illustrates the method which he proposed is as follows:
Take a basin of water, introduce into it, at two widely separated points,
the two terminals of a battery circuit which contains an interrupter,
making and breaking the circuit very rapidly. Now at two other points
touch the water with the terminals of a circuit containing a telephone. A
sound will be heard, except when the two telephone terminals touch the
water at points where the potential is the same. In this way the
equipotential lines can easily be picked out. Now to apply this to the
case of a ship at sea: Suppose one ship to be provided with a dynamo
machine generating a powerful current, and let one terminal enter the
water at the prow of the ship, and the other to be carefully insulated,
except at its end, and be trailed behind the ship, making connection with
the sea at a considerable distance from the vessel; and suppose the
current be rapidly made and broken by an interrupter; then the observer on
a second vessel provided with similar terminal conductors to the first,
but having a telephone instead of a dynamo, will be able to detect the
presence of the other vessel even at a considerable distance; and by
suitable modifications the direction of the other vessel may be found.
This conception Professor Bell has actually tried on the Potomac River
with two small boats, and found that at a mile and a quarter, the furthest
distance experimented upon, the sound due to the action of the interrupter
in one boat was distinctly audible in the other. The experiment did not
succeed quite so well in salt water. Professor Trowbridge then mentioned a
method which he had suggested some years ago for telegraphing across the
ocean without a cable, the method having been suggested more for its
interest than with any idea of its ever being put in practice. A conductor
is supposed to be laid from Labrador to Patagonia, ending in the ocean at
those points, and passing through New York, where a dynamo machine is
supposed to be included in the circuit. In Europe a line is to extend from
the north of Scotland to the south of Spain, making connections with the
ocean at those points, and in this circuit is to be included a telephone.
Then any change in the strength of the current in the American line would
produce a corresponding change in current in the European line; and thus
signals could be transmitted. Mr. Preece, of the English postal telegraph,
then gave an account of how such a system had actually been put into
practice in telegraphing between the Isle of Wight and Southampton during
a suspension in the action of the regular cable communication. The
instruments used were a telephone in one circuit, and in the other about
twenty-five Leclanche cells and an interrupter. The sound could then be
heard distinctly; and so communication was kept up until the cable was
again in working order. Of the two lines used in this case, one extended
from the sea at the end of the island near Hurst Castle, through the
length of the island, and entered the sea again at Rye; while the line on
the mainland ran from Hurst Castle, where it was connected with the sea,
through Southampton to Portsmouth, where it again entered the sea. The
distance between the two terminals at Hurst Castle was about one mile,
while that between the terminals at Portsmouth and Rye amounted to six
miles.--_Science._
* * * * *
PYROMETERS.
The accurate measurement of very high temperatures is a matter of great
importance, especially with regard to metallurgical operations; but it is
also one of great difficulty. Until recent years the only methods
suggested were to measure the expansion of a given fluid or gas, as in the
air pyrometer; or to measure the contraction of a cone of hard, burnt
clay, as in the Wedgwood pyrometer. Neither of these systems was at all
reliable or satisfactory. Lately, however, other principles have been
introduced with considerable success, and the matter is of so much
interest, not only to the practical manufacturer but also to the
physicist, that a sketch of the chief systems now in use will probably be
acceptable. He will thus be enabled to select the instrument best suited
for the particular purpose he may have in view.
The first real improvement in this direction, as in so many others, is due
to the genius of Sir William Siemens. His first attempt was a calorimetric
pyrometer, in which a mass of copper at the temperature required to be
known is thrown into the water of a calorimeter, and the heat it has
absorbed thus determined. This method, however, is not very reliable, and
was superseded by his well-known electric pyrometer. This rests on the
principle that the electric resistance of metal conductors increases with
the temperature. In the case of platinum, the metal chosen for the
purpose, this increase up to 1,500 deg.C. is very nearly in the exact
proportion of the rise of temperature. The principle is applied in the
following manner: A cylinder of fireclay slides in a metal tube, and has
two platinum wires one one-hundredth of an inch in diameter wound round it
in separate grooves. Their ends are connected at the top to two
conductors, which pass down inside the tube and end in a fireclay plug at
the bottom. The other ends of the wires are connected with a small
platinum coil, which is kept at a constant resistance. A third conductor
starting from the top of the tube passes down through it, and comes out at
the face of the metal plug. The tube is inserted in the medium whose
temperature is to be found, and the electric resistance of the coil is
measured by a differential voltameter. From this it is easy to deduce the
temperature to which the platinum has been raised. This pyrometer is
probably the most widely used at the present time.
Tremeschini's pyrometer is based on a different principle, viz., on the
expansion of a thin plate of platinum, which is heated by a mass of metal
previously raised to the temperature of the medium. The exact arrangements
are difficult to describe without the aid of drawings, but the result is
to measure the difference of temperature between the medium to be tested
and the atmosphere at the position of the instrument. The whole apparatus
is simple, compact, and easy to manage, and its indications appear to be
correct at least up to 800 deg.C.
The Trampler pyrometer is based upon the difference in the coefficients of
dilatation for iron and graphite, that of the latter being about
two-thirds that of the former. There is an iron tube containing a stick of
hard graphite. This is placed in the medium to be examined, and both
lengthen under the heat, but the iron the most of the two. At the top of
the stick of graphite is a metal cap carrying a knife-edge, on which rests
a bent lever pressed down upon it by a light spring. A fine chain attached
to the long arm of this lever is wound upon a small pulley; a larger
pulley on the same axis has wound upon it a second chain, which actuates a
third pulley on the axis of the indicating needle. In this way the
relative dilatation of the graphite is sufficiently magnified to be easily
visible.
A somewhat similar instrument is the Gauntlett pyrometer, which is largely
used in the north of England. Here the instrument is partly of iron,
partly of fireclay, and the difference in the expansion of the two
materials is caused to act by a system of springs upon a needle revolving
upon a dial.
The Ducomet pyrometer is on a very different principle, and only
applicable to rough determinations. It consists of a series of rings made
of alloys which have slightly different melting-points. These are strung
upon a rod, which is pushed into the medium to be measured, and are
pressed together by a spiral spring. As soon as any one of the rings
begins to soften under the heat, it is squeezed together by the pressure,
and, as it melts, it is completely squeezed out and disappears. The rod is
then made to rise by the thickness of the melted ring, and a simple
apparatus shows at any moment the number of rings which have melted, and
therefore the temperature which has been attained. This instrument cannot
be used to follow variations of temperature, but indicates clearly the
moment when a particular temperature is attained. It is of course entirely
dependent on the accuracy with which the melting-points of the various
alloys have been fixed.
Yet another principle is involved in the instrument called the
thalpotasimeter, which may be used either with ether, water, or mercury.
It is based on the principle that the pressure of any saturated vapor
corresponds to its temperature. The instrument consists of a tube of metal
partly filled with liquid, which is exposed to the medium which is to be
measured. A metallic pressure gauge is connected with the tube, and
indicates the pressure existing within it at any moment. By graduating the
face of the gauge when the instrument is at known temperatures, the
temperature can be read off directly from the position of the needle. From
100 deg. to 220 deg.F. ether is the liquid used, from thence to 680 deg. it is water,
and above the latter temperature mercury is employed.
Another class of pyrometers having great promise in the future is based on
what may be called the "water-current" principle. Here the temperature is
determined by noting the amount of heat communicated to a known current of
water circulating in the medium to be observed. The idea, which was due to
M. De Saintignon, has been carried out in its most improved form by M.
Boulier. Here the pyrometer itself consists of a set of tubes one inside
the other, and all inclosed for safety in a large tube of fireclay. The
central tube or pipe brings in the water from a tank above, where it is
maintained at a constant level. The water descends to the bottom of the
instrument, and opens into the end of another small tube called the
explorer (_explorateur_). This tube projects from the fireclay casing into
the medium to be examined, and can be pushed in or out as required. After
circulating through this tube the water rises again in the annular space
between the central pipe and the second pipe. The similar space between
the second pipe and the third pipe is always filled by another and much
larger current of water, which keeps the interior cool. The result is that
no loss of heat is possible in the instrument, and the water in the
central tube merely takes up just so much heat as is conducted into it
through the metal of the explorer. This heat it brings back through a
short India-rubber pipe to a casing containing a thermometer. This
thermometer is immersed in the returning current of water, and records its
temperature. It is graduated by immersing the instrument in known and
constant temperatures, and thus the graduations on the thermometer give at
once the temperature, not of the current of water, but of the medium from
which it has received its heat. In order to render the instrument
perfectly reliable, all that is necessary is that the current of water
should be always perfectly uniform, and this is easily attained by fixing
the size of the outlet once for all, and also the level of water in the
tank. So arranged, the pyrometer works with great regularity, indicating
the least variations of temperature, requiring no sort of attention, and
never suffering injury under the most intense heat; in fact the tube, when
withdrawn from the furnace, is found to be merely warm. If there is any
risk of the instrument getting broken from fall of materials or other
causes, it may be fitted with an ingenious self-acting apparatus shutting
off the supply. For this purpose the water which has passed the
thermometer is made to fall into a funnel hung on the longer arm of a
balanced lever. With an ordinary flow the water stands at a certain height
in the funnel, and, while this is so, the lever remains balanced; but if
from any accident the flow is diminished, the level of the water in the
funnel descends, the other arm of the lever falls, and in doing so
releases two springs, one of which in flying up rings a bell, and the
other by detaching a counterweight closes a cock and stops the supply of
water altogether.
It will be seen that these instruments are not adapted for shifting about
from place to place in order to observe different temperatures, but rather
for following the variations of temperature at one and the same place. For
many purposes this is of great importance. They have been used with great
success in porcelain furnaces, both at the famous manufactories at Sevres
and at another porcelain works in Limoges. From both these establishments
very favorable reports as to their working have been received.--_W.R.
Browne, in Nature_.
* * * * *
[NATURE.]
THE TEMPERATURE OF THE SOLAR SURFACE.
I have, during the summer solstice of 1884, carried out an experimental
investigation for the purpose of demonstrating the temperature of the
solar surface corresponding with the temperature transmitted to the sun
motor. Referring to the illustrations previously published, it will be
seen that the cylindrical heater of the sun motor, constructed solely for
the purpose of generating steam or expanding air, is not well adapted for
an exact determination of the amount of surface exposed to the action of
the reflected solar rays. It will be perceived on inspection that only
part of the bottom of the cylindrical heater of the motor is acted upon by
the reflected rays, and that their density diminishes _gradually_ toward
the sides of the vessel; also that owing to the imperfections of the
surface of the reflecting plates the exact course of the terminal rays
cannot be defined. Consequently, the most important point in the
investigation, namely, the area acted upon by the reflected radiant heat,
cannot be accurately determined. I have accordingly constructed an
instrument of large dimensions, a polygonal reflector (see Fig. 1),
composed of a series of inclined mirrors, and provided with a central
heater of conical form, acted upon by the reflected radiation in such a
manner that each point of its surface receives an equal amount of radiant
heat in a given time. The said reflector is contained within two regular
polygonal planes twelve inches apart, each having ninety-six sides, the
perimeter of the upper plane corresponding with a circle of eight feet
diameter, that of the lower plane being six feet. The corresponding sides
of these planes are connected by flat taper mirrors composed of thin glass
silvered on the outside. When the reflector faces the sun at right angles,
each mirror intercepts a pencil of rays of 32.61 square inches section,
hence the entire reflecting surface receives the radiant heat of an
annular sunbeam of 32.61 x 96 = 3,130 square inches section. It should be
observed that the area thus stated is 0.011 less than the total
foreshortened superficies of the ninety-six mirrors if sufficiently wide
to come in perfect contact at the vertices. Fig. 2 represents a transverse
section of the instrument as it appears when facing the sun; the direct
and reflected rays being indicated by dotted lines. The reflector and
conical heater are sustained by a flat hub and eight radial spokes bent
upward toward the ends at an angle of 45 deg.. The hub and spokes are
supported by a vertical pivot, by means of which the operator is enabled
to follow the diurnal motion of the sun, while a horizontal axle, secured
to the upper end of the pivot, and held by appropriate bearings under the
hub, enables him to regulate the inclination to correspond with the
altitude of the luminary. The heater is composed of rolled plate iron
0.017 inch thick, and provided with bead and bottom formed of
non-conducting materials. By means of a screw-plug passing through the
bottom and entering the face of the hub the heater may be applied and
removed in the course of five minutes, an important fact, as will be seen
hereafter. It is scarcely necessary to state that the proportion of the
ends of the conical heater should correspond with the perimeters of the
reflector, hence the diameter of the upper end, at the intersection of the
polygonal plane, should be to that of the lower end as 8 to 6, in order
that every part may be acted upon by reflected rays of equal density. This
condition being fulfilled, the temperature communicated will be perfectly
uniform. A short tube passes through the upper head of the heater, through
which a thermometer is inserted for measuring the internal temperature.
The stem being somewhat less than the bore of the tube, a small opening is
formed by which the necessary equilibrium of pressure will be established
with the external atmosphere. It should be mentioned that the indications
of the thermometer during the experiment have been remarkably prompt, the
bulb being subjected to the joint influence of radiation and convection.
The foregoing particulars, it will be found, furnish all necessary data
for determining with absolute precision the _diffusion_ of rays acting on
the central vessel of the solar pyrometer. But the determination of
temperature which uninterrupted solar radiation is capable of transmitting
to the polygonal reflector calls for a correct knowledge of atmospheric
absorption. Besides, an accurate estimate of the loss of radiant heat
attending the reflection of the rays by the mirrors is indispensable. Let
us consider these points separately.
[Illustration: _Fig._ 2.]
_Atmospheric Absorption._--The principal object of conducting the
investigation during the summer solstice has been the facilities afforded
for determining atmospheric absorption, the sun's zenith distance at noon
being only 17 deg. 12' at New York. The retardation of the sun's rays in
passing through a clear atmosphere obviously depends on the depth
penetrated; hence--neglecting the curvature of the atmospheric limit--the
retardation will be as the secants of the zenith distances. Accordingly,
an observation of the temperature produced by solar radiation at a zenith
distance whose secant is _twice_ that of the secant of 17 deg. 12', viz., 61 deg.
28', determines the minimum atmospheric absorption at New York. The result
of observations conducted during a series of years shows that the maximum
solar intensity at 17 deg. 12' reaches 66.2 deg. F., while at a zenith distance of
61 deg. 28' it is 52.5 deg. F.; hence, minimum atmospheric absorption at New York,
during the summer solstice,
13.7
is 66.2 deg.-52.5 deg. = 13.7 deg. F., or ------ = 0.207 of the sun's
66.2
radiant energy where the rays enter the terrestrial atmosphere.
[Illustration: CAPTAIN ERICSSON'S SOLAR PYROMETER, ERECTED AT NEW YORK,
1884.]
In order to determine the loss of energy attending the reflection of the
rays by the diagonal mirrors, I have constructed a special apparatus,
which, by means of a parallactic mechanism, faces the sun at right angles
during observations. It consists principally of two small mirrors,
manufactured of the same materials as the reflector, placed diagonally at
right angles to each other; a thermometer being applied between the two,
whose stem points toward the sun. The direct solar rays entering through
perforations of an appropriate shade, and reflected by the inclined
mirrors, act simultaneously on opposite sides of the bulb. The mean result
of repeated trials, all differing but slightly, show that the energy of
the direct solar rays acting on the polygonal reflector is reduced 0.235
before reaching the heater.
In accordance with the previous article, the investigation has been based
on the assumption that _the temperatures produced by radiant heat at given
distances from its source are inversely as the diffusion of the rays at
those distances. In other words, the temperature produced by solar
radiation is as the density of the rays._
It will be remembered that Sir Isaac Newton, in estimating the temperature
to which the comet of 1680 was subjected when nearest to the sun, based
his calculations on the result of his practical observations that the
maximum temperature produced by solar radiation was one-third of that of
boiling water. Modern research shows that the observer of 1680 underrated
solar intensity only 5 deg. for the latitude of London. The distance of the
comet from the center of the sun being to the distance of the earth from
the same as 6 to 1,000, the author of the "Principia" asserted that the
density of the rays was as 1,000 squared to 6 squared = 28,000 to 1; hence the comet was
subjected to a temperature of 28,000 x 180 deg./3 = 1,680,000 deg., an intensity
exactly "2,000 times greater than that of red-hot iron" at a temperature
of 840 deg.. The distance of the comet from the solar surface being equal to
one-third of the sun's radius, it will be seen that, in accordance with
the Newtonian doctrine, the temperature to which it was subjected
indicated a solar intensity of
4 squared x 1,680,000
-------------- = 2,986,000 deg. F.
3
The writer has established the correctness of the assumption that "the
temperature is as the density of the rays," by showing practically that
the _diminution_ of solar temperature (for corresponding zenith distances)
when the earth is in aphelion corresponds with the increased diffusion of
the rays consequent on increased distance from the sun. This practical
demonstration, however, has been questioned on the insufficient ground
that "the eccentricity of the earth's orbit is too small and the
temperature produced by solar radiation too low" to furnish a safe basis
for computations of solar temperature.
In order to meet the objection that the diffusion of the rays in aphelion
do not differ sufficiently, the solar pyrometer has been so arranged that
the density, _i. e._, the diffusion of the reflected rays, can be changed
from a ratio of 1 in 5,040 to that of 1 in 10,241. This has been effected
by employing heaters respectively 10 inches and 20 inches in diameter.
With reference to the "low" solar temperature pointed out, it will be
perceived that the adopted expedient of increasing the density of the rays
without raising the temperature by _converging_ radiation, removes the
objection urged.
Agreeably to the dimensions already specified, the area of the 10-inch
heater acted upon by the reflected solar rays is 331.65 square inches, the
area of the 20-inch heater being 673.9 square inches. The section of the
annular sunbeam whose direct rays act upon the polygonal reflector is
3,130 square inches, as before stated.
Regarding the diffusion of the solar rays during the investigation, the
following demonstration will be readily understood. The area of a sphere
whose radius is equal to the earth's distance from the sun in aphelion
being to the sun's area as 218.1 squared to 1, while the reflecter of the solar
pyrometer intercepts a sunbeam of 3,130 square inches section, it follows
that the reflector will receive the radiant heat developed by 3,130 /
218.1 squared = 0.0658 square inch of the solar surface. Hence, as the 10-inch
heater presents an area of 331.65 square inches, we establish the fact
that the reflected solar rays, acting on the same, are _diffused_ in the
ratio of 331.65 to 0.0658, or 331.65 / 0.0658 = 5,040 to 1; the diffusion
of the rays acting on the 20-inch heater being as 673.9 to 0.0658, or
673.9 / 0.0658 = 10,241 to 1.
The atmospheric conditions having proved unfavorable during the
investigation, maximum solar temperature was not recorded. Accordingly,
the heaters of the solar pyrometer did not reach maximum temperature, the
highest indication by the thermometer of the small heater being 336.5 deg.,
that of the large one being 200.5 deg. above the surrounding air. No
compensation will, however, be introduced on account of deficient solar
heat, the intention being to base the computation of solar temperature
solely on the result of observations conducted at New York during the
summer solstice of 1884. It will be noticed that the temperature of the
large heater is proportionally higher than that of the small heater, a
fact showing that the latter, owing to its higher temperature, loses more
heat by radiation and convection than the former. Besides, the rate of
cooling of heated bodies increases more rapidly than the augmentation of
temperature.
The loss occasioned by the imperfect reflection of the mirrors, as before
stated, is 0.235 of the energy transmitted by the direct solar rays acting
on the polygonal reflector, hence the temperature which the solar rays are
capable of imparting to the large heater will be 200.5 deg. x 1.235 =
247.617 deg.; but the energy of the solar rays acting on the _reflector_ is
reduced 0.207 by atmospheric absorption, consequently the ultimate
temperature which the sun's radiant energy is capable of imparting to the
heater is 1.207 x 247.617 deg. = 298.87 deg. F. It is hardly necessary to observe
that this temperature (developed by solar radiation diffused fully
ten-thousandfold) must be regarded as an _actual_ temperature, since a
perfectly transparent atmosphere, and a reflector capable of transmitting
the whole energy of the sun's rays to the heater, would produce the same.
The result of the experimental investigation carried out during the summer
solstice of 1884 may be thus briefly stated. The diffusion of the solar
rays acting on the 20 inch heater being in the ratio of 1 to 10,241, the
temperature of the solar surface cannot be less than 298.87 deg. x 10,241 =
3,060,727 deg. F. This underrated computation must be accepted unless it can
be shown that the temperature produced by radiant heat is not inversely as
the diffusion of the rays. Physicists who question the existence of such
high solar temperature should bear in mind that in consequence of the
great attraction of the solar mass, hydrogen on the sun's surface raised
to a temperature of 4,000 deg. C. will be nearly twice as heavy as hydrogen on
the surface of the earth at ordinary atmospheric temperatures; and that,
owing to the immense depth of the solar atmosphere, its density would be
so enormous at the stated low temperature that the observed rapid
movements within the solar envelope could not possibly take place. It
scarcely needs demonstration to prove that extreme tenuity can alone
account for the extraordinary velocities recorded by observers of solar
phenomena. But _extreme tenuity_ is incompatible with low temperature and
the pressure produced by an atmospheric column probably exceeding 50,000
miles in height subjected to the sun's powerful attraction, diminished
only one-fourth at the stated elevation. These facts warrant the
conclusion that the high temperature established by our investigation is
requisite to prevent undue density of the solar atmosphere.
It is not intended at present to discuss the necessity of tenuity with
reference to the functions of the sun as a radiator; yet it will be proper
to observe that on merely dynamical grounds the enormous density of the
solar envelope which would result from low temperature presents an
unanswerable objection to the assumption of Pouillet, Vicaire,
Sainte-Claire Deville, and other eminent _savants_, that the temperature
of the solar surface does not reach 3,000 deg. C.
J. ERICSSON.
* * * * *
CHEMICAL NATURE OF STARCH GRAINS.
Dr. Brukner has contributed to the _Proceedings_ of the Vienna Academy of
Sciences a paper on the "Chemical Nature of the Different Varieties of
Starch," especially in reference to the question whether the granulose of
Nageli, the soluble starch of Jessen, the amylodextrin of W. Nageli, and
the amidulin of Nasse are the same or different substances. A single
experiment will serve to show that under certain conditions a soluble
substance maybe obtained from starch grains.
If dried starch grains are rubbed between two glass plates, the grains
will be seen under the microscope to be fissured, and if then wetted and
filtered, the filtrate will be a perfectly clear liquid showing a strong
starch reaction with iodine. Since no solution is obtained from uninjured
grains, even after soaking for weeks in water, Brukner concludes that the
outer layers of the starch grains form a membrane protecting the interior
soluble layers from the action of the water.
The soluble filtrate from starch paste also contains a substance identical
with granulose. Between the two kinds of starch, the granular and that
contained in paste, there is no chemical but only a physical difference,
depending on the condition of aggregation of their micellae.
W. Nageli maintains that granulose, or soluble starch, differs from
amylodextrin in the former being precipitated by tannic acid and acetate
of lead, while the latter is not. Brukner fails to confirm this
difference, obtaining a voluminous precipitate with tannic acid and
acetate of lead in the case of both substances. Another difference
maintained by Nageli, that freshly precipitated starch is insoluble,
amylodextrin soluble in water, is also contested; the author finding that
granulose is soluble to a considerable extent in water, not only
immediately after precipitation, but when it has remained for twenty-four
hours under absolute alcohol. Other differences pointed out by W. Nageli,
Brukner also maintains to be non-existent, and he regards amidulin and
amylodextrin as identical. Brucke gave the name erythrogranulose to a
substance nearly related to granulose, but with a stronger affinity for
iodine, and receiving from it not a blue but a red color. Brukner regards
the red color as resulting from a mixture of erythrodextrin, and the
greater solubility of this substance in water.
If a mixture of filtered potato starch paste and erythrodextrin is dried
in a watch glass covered with a thin pellicle of collodion, and a drop of
iodine solution placed on the latter, it penetrates very slowly through
the pellicle, the dextrin becoming first tinctured with red, and the
granulose afterward with blue. If, on the other hand, no erythrodextrin is
used, the diffusion of the iodine causes at once simply a blue coloring.
With regard to the iodine reaction of starch, Brukner contests Sachsse's
view as to the loss of color of iodide of starch at a high temperature. He
shows that the iodide may resist heat, and that the loss of color depends
on the greater attraction of water for iodine as compared with starch, and
the greater solubility of iodine in water at high temperatures.
The different kinds of starch do not take the same tint with the same
quantity of (solid) iodine. That from the potato _arum_ gives a blue, and
that from wheat and rice a violet tint; while the filtrate from starch
paste, from whatever source, always gives a blue color.
* * * * *
THE AMALGAMATION OF SILVER ORES.
DESCRIPTION OF THE FRANCKE "TINA" OR VAT PROCESS FOR THE AMALGAMATION OF
SILVER ORES.
[Footnote: Paper read before the Institution of Mechanical Engineers at
the Cardiff meeting.--_Engineering_.]
By Mr. EDGAR P. RATHBONE, of London.
In the year 1882, while on a visit to some of the great silver mines in
Bolivia, an opportunity was afforded the writer of inspecting a new and
successful process for the treatment of silver ores, the invention of Herr
Francke, a German gentleman long resident in Bolivia, whose acquaintance
the writer had also the pleasure of making. After many years of tedious
working devoted to experiments bearing on the metallurgical treatment of
rich but refractory silver ores, the inventor has successfully introduced
the process of which it is proposed in this paper to give a description,
and which has, by its satisfactory working, entirely eclipsed all other
plans hitherto tried in Bolivia, Peru, and Chili. The Francke "tina"
process is based on the same metallurgical principles as the system
described by Alonzo Barba in 1640, and also on those introduced into the
States in more recent times under the name of the Washoe process.[1]
[Footnote 1: Transactions of the American Institute of Mining Engineers,
vol. ii., p. 159.]
It was only after a long and careful study of these two processes, and by
making close observations and experiments on other plans, which had up to
that time been tried with more or less success in Bolivia, Peru, and
Chili--such as the Mexican amalgamation process, technically known as the
"patio" process; the improved Freiberg barrel amalgamation process; as
used at Copiapo; and the "Kronke" process--that Herr Francke eventually
succeeded in devising his new process, and by its means treating
economically the rich but refractory silver ores, such as those found at
the celebrated Huanchaca and Guadalupe mines in Potosi, Bolivia. In this
description of the process the writer will endeavor to enter into every
possible detail having a practical bearing on the final results; and with
this view he commences with the actual separation of the ores at the
mines.
_Ore Dressing, etc._--This consists simply in the separation of the ore by
hand at the mines into different qualities, by women and boys with small
hammers, the process being that known as "cobbing" in Cornwall. The object
of this separation is twofold: first to separate the rich parts from the
poor as they come together in the same lump of ore, otherwise rich pieces
might go undetected; and, secondly, to reduce the whole body of ore coming
from the mine to such convenient size as permits of its being fed directly
into the stamps battery. The reason for this separation not being effected
by those mechanical appliances so common in most ore dressing
establishments, such as stone breakers or crushing rolls, is simply
because the ores are so rich in silver, and frequently of such a brittle
nature, that any undue pulverization would certainly result in a great
loss of silver, as a large amount would be carried away in the form of
fine dust. So much attention is indeed required in this department that it
is found requisite to institute strict superintendence in the sorting or
cobbing sheds, in order to prevent as far as practicable any improper
diminution of the ores. According to the above method, the ores coming
from the mine are classified into the four following divisions:
1. Very rich ore, averaging about six per cent. of silver, or containing
say 2,000 ounces of silver to the ton (of 2,000 lb.).
2. Rich ore, averaging about one per cent. of silver, or say from 300 to
400 ounces of silver to the ton.
3. Ordinary ore, averaging about 1/2 per cent. of silver, or say from 150
oz. to 200 oz. of silver to the ton.
4. Gangue, or waste rock, thrown on the dump heaps.
The first of these qualities--the very rich ore--is so valuable as to
render advantageous its direct export in the raw state to the coast for
shipment to Europe. The cost of fuel in Bolivia forms so considerable a
charge in smelting operations, that the cost of freight to Europe on very
rich silver ores works out at a relatively insignificant figure, when
compared with the cost of smelting operations in that country. This rich
ore is consequently selected very carefully, and packed up in tough
rawhide bags, so as to make small compact parcels some 18 in. to 2 ft.
long, and 8 in. to 12 in. thick, each containing about 1 cwt. Two of such
bags form a mule load, slung across the animal's back.
The second and third qualities of ore are taken direct to the smelting
works; and where these are situated at some distance from the mines, as at
Huanchaca and Guadalupe, the transport is effected by means of strong but
lightly built iron carts, specially constructed to meet the heavy wear and
tear consequent upon the rough mountain roads. These two classes of ores
are either treated separately, or mixed together in such proportion as is
found by experience to be most suitable for the smelting process.
On its arrival at the reduction works the ore is taken direct to the stamp
mill. At the Huanchaca works there are sixty-five heads of stamps, each
head weighing about 500 lb., with five heads in each battery, and crushing
about 50 cwt. per head per twenty-four hours. The ore is stamped dry,
without water, requiring no coffers; this is a decided advantage as
regards first cost, owing to the great weight of the coffers, from 2 to 3
tons--a very heavy item when the cost of transport from Europe at about
50_l_. per ton is considered. As fast as the ore is stamped, it is
shoveled out by hand, and thrown upon inclined sieves of forty holes per
lineal inch; the stuff which will not pass through the mesh is returned to
the stamps.
Dry stamping may be said to be almost a necessity in dealing with these
rich silver ores, as with the employment of water there is a great loss of
silver, owing to the finer particles being carried away in suspension, and
thus getting mixed with the slimes, from which it is exceedingly difficult
to recover them, especially in those remote regions where the cost of
maintaining large ore-dressing establishments is very heavy. Dry stamping,
however, presents many serious drawbacks, some of which could probably be
eliminated if they received proper attention. For instance, the very fine
dust, which rises in a dense cloud during the operation of stamping, not
only settles down on all parts of the machinery, interfering with its
proper working, so that some part of the battery is nearly always stopped
for repairs, but is also the cause of serious inconvenience to the
workmen. At the Huanchaca mines, owing to the presence of galena or
sulphide of lead in the ores, this fine dust is of such an injurious
character as not unfrequently to cause the death of the workmen; as a
precautionary measure they are accustomed to stuff cotton wool into their
nostrils. This, however, is only a partial preventive; and the men find
the best method of overcoming the evil effect is to return to their homes
at intervals of a few weeks, their places being taken by others for the
same periods. In dry stamping there is also a considerable loss of silver
in the fine particles of rich ore which are carried away as dust and
irrevocably lost. To prevent this loss, the writer proposed while at
Huanchaca that a chamber should be constructed, into which all the fine
dust might be exhausted or blown by a powerful fan or ventilator.
_Roasting_.--From the stamps the stamped ore is taken in small ore cars to
the roasting furnaces, which are double bedded in design, one hearth being
built immediately above the other. This type of furnace has proved, after
various trials, to be that best suited for the treatment of the Bolivian
silver ores, and is stated to have been found the most economical as
regards consumption of fuel, and to give the least trouble in labor.
At the Huanchaca mines these furnaces cost about 100_l_. each, and are
capable of roasting from 2 to 21/2 tons of ore in twenty-four hours, the
quantity and cost of the fuel consumed being as follows:
Bolivian dollars at 3s. 1d.
Tola (a kind of shrub), 3 cwt., at 60 cents. 1.80
Yareta (a resinous moss), 4 cwt., at 80 cents. 3.20
Torba (turf), 10 cwt., at 40 cents. 4.00
----
Bolivian dollars. 9.00, say 28s.
One man can attend to two furnaces, and earns 3s. per shift of twelve
hours.
Probably no revolving mechanical furnace is suited to the roasting of
these ores, as the operation requires to be carefully and intelligently
watched, for it is essential to the success of the Francke process that
the ores should not be completely or "dead" roasted, inasmuch as certain
salts, prejudicial to the ultimate proper working of the process, are
liable to be formed if the roasting be too protracted. These salts are
mainly due to the presence of antimony, zinc, lead, and arsenic, all of
which are unfavorable to amalgamation.
The ores are roasted with 8 per cent. of salt, or 400 lb. of salt for the
charge of 21/2 tons of ore; the salt costs 70 cents, or 2s. 2d. per 100 lb.
So roasted the ores are only partially chlorinized, and their complete
chlorination is effected subsequently, during the process of amalgamation;
the chlorides are thus formed progressively as required, and, in fact, it
would almost appear that the success of the process virtually consists in
obviating the formation of injurious salts. All the sulphide ores in
Bolivia contain sufficient copper to form the quantity of cuprous chloride
requisite for the first stages of roasting, in order to render the silver
contained in the ore thoroughly amenable to subsequent amalgamation.
_Amalgamating_.--From the furnaces the roasted ore is taken in ore cars to
large hoppers or bins situated immediately behind the grinding and
amalgamating vats, locally known as "tinas," into which the ore is run
from the bin through a chute fitted with a regulating slide. The tinas or
amalgamating vats constitute the prominent feature of the Francke process;
they are large wooden vats, shown in Figs. 1 and 2, page 173, from 6 ft.
to 10 ft. in diameter and 5 ft. deep, capacious enough to treat about 21/2
tons of ore at a time. Each vat is very strongly constructed, being bound
with thick iron hoops. At the bottom it is fitted with copper plates about
3 in. thick, A in Fig. 1; and at intervals round the sides of the vat are
fixed copper plates, as shown in Figs. 3 and 4, with ribs on their inner
faces, slightly inclined to the horizontal, for promoting a more thorough
mixing. It is considered essential to the success of the process that the
bottom plates should present a clear rubbing surface of at least 10 square
feet.
[Illustration: THE FRANCKE "TINA" PROCESS FOR THE AMALGAMATION OF SILVER
ORES.]
Within the vat, and working on the top of the copper plates, there is a
heavy copper stirrer or muller, B, Figs. 1 and 2, caused to revolve by the
shafting, C, at the rate of 45 revolutions per minute. At Huanchaca this
stirrer has been made with four projecting radial arms, D D, Figs. 1 and
2; but at Guadalupe it is composed of one single bell-shaped piece, Figs.
3 and 4, without any arms, but with slabs like arms fixed on its
underside; and this latter is claimed to be the most effective. The
stirrer can be lifted or depressed in the vat at will by means of a worm
and screw at the top of the driving shaft, Fig. 3.
The bevel gearing is revolved by shafting connected with pulley wheels and
belting, the wheels being 3 ft. and 11/2 ft. in diameter, and 6 in. broad.
The driving engine is placed at one end of the building. Each vat requires
from 21/2 to 3 horse-power, or in other words, an expenditure of 1
horse-power per ton of ore treated.
At the bottom of the vat, and in front of it, a large wooden stop-cock is
fitted, through which the liquid amalgam is drawn off at the end of the
process into another shallow-bottomed and smaller vat, Figs. 1 and 2.
Directly above this last vat there is a water hose, supplied with a
flexible spout, through which a strong stream of water is directed upon
the amalgam as it issues from the grinding vat, in order to wash off all
impurities.
The following is the mode of working usually employed. The grinding vat or
tina is first charged to about one-fifth of its depth with water and from
6 cwt. to 7 cwt. of common salt. The amount of salt required in the
process depends naturally on the character of the ore to be treated, as
ascertained by actual experiment, and averages from 150 lb. to 300 lb. per
ton of ore. Into this brine a jet of steam is then directed, and the
stirrer is set to work for about half an hour, until the liquid is in a
thoroughly boiling condition, in which state it must be kept until the end
of the process.
As soon as the liquid reaches boiling point, the stamped and roasted ore
is run into the vat, and at the end of another half-hour about 1 cwt. of
mercury is added, further quantities being added as required at different
stages of the process. The stirring is kept up continuously for eight to
twelve hours, according to the character and richness of the ores. At the
end of this time the amalgam is run out through the stop-cock at bottom of
the vat, is washed, and is put into hydraulic presses, by means of which
the mercury is squeezed out, leaving behind a thick, pulpy mass, composed
mainly of silver, and locally termed a "pina," from its resembling in
shape the cone of a pine tree. These pinas are then carefully weighed and
put into a subliming furnace, Figs. 5 and 6, in order to drive off the
rest of the mercury, the silver being subsequently run into bars. About
four ounces of mercury are lost for every pound of silver made.
The actual quantities of mercury to be added in the grinding vat, and the
times of its addition, are based entirely on practical experience of the
process. With ore assaying 150 oz. to 175 oz. of silver to the ton, 75
lb. of mercury are put in at the commencement, another 75 lb. at intervals
during the middle of the process, and finally another lot of 75 lb.
shortly before the termination. When treating "pacos," or earthy chlorides
of silver, assaying only 20 oz. to 30 oz. of silver to the ton, 36 lb. of
mercury is added to 21/2 tons of ore at three different stages of the
process as just described.
The _rationale_ of the process therefore appears to be that the
chlorination of the ores is only partially effected during the roasting,
so as to prevent the formation of injurious salts, and is completed in the
vats, in which the chloride of copper is formed progressively as required,
by the gradual grinding away of the copper by friction between the bottom
copper plates and the stirrer; and this chloride subsequently becoming
incorporated with the boiling brine is considered to quicken the action of
the mercury upon the silver.
_Subliming_.--The subliming furnace, shown in Figs. 5 and 6, is a plain
cylindrical chamber, A, about 4 ft. diameter inside and 41/2 ft. high, lined
with firebrick, in the center of which is fixed the upright cast-iron
cylinder or retort, C, of 1 ft. diameter, closed at top and open at
bottom. The furnace top is closed by a cast-iron lid, which is lifted off
for charging the fuel. Round the top of the furnace is a tier of radial
outlet holes for the fuel smoke to escape through; and round the bottom is
a corresponding tier of inlet air-holes, through which the fuel is
continually rabbled with poles by hand. The fuel used is llama dung,
costing 80 cents, or 2s. 6d., per 250 lb.; it makes a very excellent fuel
for smelting purposes, smouldering and maintaining steadily the low heat
required for subliming the mercury from the amalgam. Beneath the furnace
is a vault containing a wrought-iron water-tank, B, into which the open
mouth of the retort, C, projects downward and is submerged below the
water. For charging the retort, the water-tank is placed on a trolly; and
standing upright on a stool inside the tank is placed the pina, or conical
mass of silver amalgam, which is held together by being built up on a
core-bar fitted with a series of horizontal disks. The trolly is then run
into the vault, and the water-tank containing the pina is lifted by
screw-jacks, so as to raise the pina into the retort, in which position
the tank is then supported by a cross-beam. The sublimed mercury is
condensed and collected in the water; and on the completion of the process
the tank is lowered, and the spongy or porous cone of silver is withdrawn
from the retort. The subliming furnaces are ranged in a row, and
communicate by lines of rails with the weigh-house.
* * * * *
INTERESTING FACTS ABOUT PLATINUM.
After an excellent day of weakfishing on Barnegat Bay and an exceptionable
supper of the good, old fashioned, country tavern kind, a social party of
anglers sat about on Uncle Jo Parker's broad porch at Forked River,
smoking and enjoying the cool, fragrant breath of the cedar swamp, when
somehow the chat drifted to the subject of assaying and refining the
precious metals. That was just where one of the party, Mr. D.W. Baker, of
Newark, was at home, and in the course of an impromptu lecture he told the
party more about the topic under discussion, and especially the platinum
branch of it, than they ever knew before.
"Our firm," he said, "practically does all the platinum business of this
country, and the demand for the material is so great that we never can get
more than we want of it. The principal portion, or, in fact, nearly all of
it, comes from the famous mines of the Demidoff family, who have the
monopoly of the production in Russia. It is all refined and made into
sheets of various thicknesses, and into wire of certain commercial sizes,
before it comes to us; but we have frequently to cut, roll, and redraw it
to new forms and sizes to meet the demands upon us. At one time it was
coined in Russia, but it is no longer applied to that use. We have
obtained some very good crude platinum ore from South America and have
refined it successfully, but the supply from that source is, as yet, very
small. I am not aware that it has been found anywhere else than in
Colombia, on that continent, but the explorations thus far made into the
mineral resources of South America have been very meager, and it is by no
means improbable that platinum may yet be discovered there in quantities
rivaling the supply of Russia.
"A popular error respecting platinum is that its intrinsic value is the
same as that of gold. At one time it did approximate to gold in value, but
never quite reached it, and is now worth only $8 to $12 an ounce,
according to the work expended upon it in getting it into required forms
and the amount of alloy it contains. The alloy used for it is iridium,
which hardens it, and the more iridium it contains the more difficult it
is to work, and consequently the more expensive. When pure, platinum is as
soft as silver, but by the addition of iridium it becomes the hardest of
metals. The great difficulty in manipulating platinum is its excessive
resistance to heat. A temperature that will make steel run like water and
melt down fireclay has absolutely no effect upon it. You may put a piece
of platinum wire no thicker than human hair into a blast furnace where
ingots of steel are melting down all around it, and the bit of wire will
come out as absolutely unchanged as if it had been in an ice box all the
time.
"No means has been discovered for accurately determining the melting
temperature of platinum, but it must be enormous. And yet, if you put a
bit of lead into the crucible with the platinum, both metals will melt
down together at the low temperature that fuses the lead, and if you try
to melt lead in a platinum crucible, you will find that as soon as the
lead melts the platinum with which it comes into contact also melts and
your crucible is destroyed.
"A distinguishing characteristic of platinum is its extreme ductility. A
wire can be made from it finer than from any other metal. I have a sample
in my pocket, the gauge of which is only one two-thousandth of an inch,
and it is practicable to make it thinner. It has even been affirmed that
platinum wire has been made so fine as to be invisible to the naked eye,
but that I do not state as of my own knowledge. This wire my son made."
Mr. Baker exhibited the sample spoken of. It looked like a tress of silky
hair, and had it not been shown upon a piece of black paper could hardly
have been seen. He went on:
"The draw plates, by means of which these fine wires are made, are
sapphires and rubies. You may fancy for yourselves how extremely delicate
must be the work of making holes of such exceeding smallness to accurate
gauge, too, in those very hard stones. I get all my draw plates from an
old Swiss lady in New York, who makes them herself to order. But, delicate
as is the work of boring the holes, there is something still more delicate
in the processes that produce such fine wire as this. That something is
the filing of a long point on the wire to enable the poking of the end of
it through the draw plate so that it can be caught by the nippers. Imagine
yourself filing a long, tapering point on the end of a wire only one
eighteen-hundredths of an inch in diameter, in order to get it through a
draw plate that will bring it down to one two-thousandths. My son does
that without using a magnifying glass. I cannot say positively what uses
this very thin wire is put to, but something in surgery, I believe, either
for fastening together portions of bone or for operations. A newly
invented instrument has been described to me, which, if it does what has
been affirmed, is one of the greatest and most wonderful discoveries of
modern science. A very thin platinum wire loop, brought to incandescence
by the current from a battery--which, though of great power, is so small
that it hangs from the lapel of the operator's coat--is used instead of a
knife for excisions and certain amputations. It sears as it cuts, prevents
the loss of blood, and is absolutely painless, which is the most
astonishing thing about it.
"Our greatest consumers of platinum are the electricians, particularly the
incandescent light companies. I supply the platinum wire for both the
Edison and the Maxim companies, and the quantity they require so
constantly increases that the demand threatens to exceed the supply of the
metal. Sheets of platinum are bought by chemists, who have them converted
into crucibles and other forms."
The reporter's curiosity was awakened by Mr. Baker's mention of the old
lady who made those very fine draw plates, and on his return to the city
he hunted her up. Mrs. Francis A. Jeannot, the lady in question, was found
in neat apartments in a handsome flat in West Fifty-first street. Age has
silvered her hair, but her eyes are still bright, and her movements
indicate elasticity and strength. She is a native of Neufchatel,
Switzerland, and speaks English with a little difficulty, but whenever the
reporter's English was a little hard for her a very pretty girl with
brilliant eyes and crinkly jet-black hair, who subsequently proved to be a
daughter of Mrs. Jeannot, came to the rescue. With the girl's occasional
aid, the old lady's story was as follows:
"I have been in this business for thirty years. I learned it when I was a
girl in Switzerland. Very few in this country know anything correctly
about it. Numbers of people endeavor to find it out, and they experiment
to learn it, especially to do it by machinery, but without success. But,
ah, me! It is no longer a business that is anything worth. Thirty years
ago many stone draw plates were wanted, for then there was a great deal
done in filigree gold jewelry. Then the plates were worth from $2.50 up to
as high as $15, according to the magnitude of the stones and the size of
the holes I bored in them. Now, however, all that good time is past.
Nobody wants filigree gold jewelry any more, and there is so little demand
for fine wire of the precious metals that few draw plates are desired. The
prices now are no more than from $1.25 up to say $8, but it is very rare
that one is required the cost of which is more than $4. And of that a very
large part must go to the lapidary to pay for the stone and for his work
in cutting it to an even round disk. Then, what I get for the long and
hard work of boring the stone by hand is very little. 'By hand?' Oh, yes.
That must always be the only good way. The work of the machine is not
perfect. It never produces such good plates as are made by the hand and
eye of the trained artisan. 'How are they bored?' Ah, sir, you must excuse
me that I do not tell you that. It is simple, but there is just a little
of it that is a secret, and that little makes a vast difference between
producing work which is good and that which is not. It has cost me no
little to learn it, and while it is worth very little just now, perhaps
fashion may change, and plates may be wanted to make gold wire again to an
extent that may be profitable. I do not wish to tell everybody that which
will deprive me of the little advantage my knowledge gives me. 'The
stones?' Oh, we of course do not use finely colored ones. They are too
valuable. But those that we employ must be genuine sapphires and rubies,
sound and without flaws. Here are some. You see they look like only
irregular lumps of muddy-tinted broken glass. Here is a finished one."
The old lady exhibited a piece of solid brass about an inch long,
three-quarters of an inch in width, and one-sixteenth in thickness. In its
center was a small disk of stone with a hole through it, a hole that was
very smooth, wide on one side and hardly perceptible on the other. The
stone was sunk deep into the brass and bedded firmly in it. She went on:
"You will find, if you try, that you can with difficulty push through that
hole a hair from your beard. But, small as it is, it must be perfectly
smooth, and of an accurate gauge. I do not any longer myself set the
stones in the brass, as I am not so strong as I once was. My son does that
for me. But neither he nor my daughter, nor anybody else in this country,
I believe, can bore the holes so well as I can even yet. 'How long does a
draw plate last?' Ah! Practically forever. Except by clumsy handling or
accident, it does not need to be replaced, at least in one lifetime. And
there is another reason why I sell so few now. Those who require them are
supplied. 'Watch jewels?' Yes, I used to make them, but do so no longer.
They can be imported from Europe at the price of $1 a dozen, and at such a
figure one could not earn bread in making them here."--_Manuf. Gazette._
* * * * *
BAYLE'S LAMP CHIMNEY.
The different types of lamps used in domestic lighting present several
imperfections, and daily experience shows too often how difficult it is,
even with the most careful and best studied models, to have a perfect
combustion of the usual liquids--oil, kerosene, etc.
[Illustration: BAYLE'S NEW LAMP CHIMNEY.]
Mr. P. Bayle has endeavored to remedy this state of things by experiments
upon the chimney, inasmuch as he could not think of modifying the
arrangements of the lamps of commerce "without injury to man" interests,
and encountering material difficulties.
The chimney is not only an apparatus designed to carry off the smoke and
gases due to combustion, for its principal role is to break the
equilibrium of the atmospheric air, which is the great reservoir of
oxygen, and to suck into the flame, through the difference of densities,
this indispensable agent to combustion. The lamps which we now use are
provided with cylindrical chimneys either with or without a shoulder at
the base. The shouldered chimney would be sufficient to suck in the
quantity of air necessary for a good combustion if we could at will
increase its dimensions in the direction of the diameter or height. But,
on account of the fragile nature of the material of which it consists, as
also because of the arrangement of the lighting apparatus, we are forced
lo give the chimney limited dimensions. The result is an insufficient
draught, and consequently an imperfect combustion. It became a question,
then, of finding a chimney which, with small dimensions, should have great
suctional power. Mr. Bayle has taken advantage of the properties of
convergent-divergent ajutages, and of the discovery of Mr. Romilly that a
current of gas directed into the axis and toward the small base of a
truncated cone, at a definite distance therefrom, has the property of
drawing along with it a quantity of air nearly double that which this same
current could carry along if it were directed toward a cylinder. In
getting up his new chimney, Mr. Bayle has utilized these principles as
follows: Round-burner lamps have, as well known, two currents of air--an
internal current which traverses the small tube that carries the wick, and
an external one which passes under the chimney-holder externally to the
wick. In giving the upper part of the chimney, properly so called, the
form of a truncated cone whose smaller base is turned toward the internal
current of air, that is to say, in directing this current toward the
contracted part of the upper cone, at the point where the depression is
greatest, a strong suction is brought about, which has the effect of
carrying along the air between the wick and glass, and giving it its own
velocity. The draught of the two currents having been effected through the
conical form of the upper part of the chimney, it remained to regulate the
entrance of the external current into the flame. If this current should
enter the latter at too sharp an angle, it would carry it toward the mouth
of the chimney before the chemical combustion of the carbon and oxygen was
finished; and if, on the contrary, it should traverse it at too obtuse an
angle, it would depress and contract it. Experience has shown that in the
majority of cases the most favorable angle at which the external current
of air can be led into the flame varies between 35 deg. and 45 deg.. We say in the
majority of cases, for there are exceptions; this depends upon the
combustive materials and upon the conditions under which they enter the
flame. The annexed figure shows the form adopted by the inventor for oil
and kerosene lamps. As may be seen, the chimney consists of two cones, A
and B, connected end to end by their small bases. The upper one, A, or
divergent cone, is constructed according to a variable angle, but one
which, in order to produce its maximum effect, ought not to differ much
from 5 deg.. This cone rests upon the convergent one, B, whose angle, as we
have said, varies between 35 deg. and 45 deg.. To the large base of this cone
there is soldered a cylindrical part, c, designed for fixing the chimney
to the holder. The height given the divergent cone is likewise variable,
but a very beautiful light is obtained, when it is equal to six times the
diameter of the contracted part. When the lamp is designed to be used in a
still atmosphere, free from abrupt currents of air, the height may be
reduced to four times the diameter of the base, without the light being
thereby rendered any the less bright. As for the height to be given the
convergent cone, B, that is determined by the opening of the angle
according to which it has been constructed. Finally, as a general thing,
the diameter of the small base should be equal to half the large base of
the convergent cone, B.
The new chimney should be placed upon the holder in such a way that the
upper part of the wick tube, D, is a few millimeters beneath the base of
the convergent cone. The height to be given the wick varies according to
the lamp used. It is regulated so as to obtain a steady and regular
combustion. In oil lamps it must project about 11/2 centimeters. If two
lamps of the same size be observed, one of which is fitted with the new
chimney and the other with the old style, we shall be struck with the
difference that exists in the color of the flame as well as in its
intensity. While in the case of the cylindrical glass the flame is red and
dull, in that of the circuit it is white and very bright. This, however,
is not surprising when we reflect upon the theoretical conditions upon
which the construction of the new chimney is based--the strong influx of
air having the result of causing a more active combustion of the liquid,
and consequently of raising to white heat the particles of carbon
disseminated through the flame. As it was of interest to ascertain what
the increase of illuminating power was in a given lamp provided with the
new chimney, Mr. Felix le Blanc undertook some photometric experiments.
The trials were made with a Gagneau lamp provided with a chimney of the
ordinary shape, and then with one of Mr. Bayle's. The measurements were
made after each had been burned half an hour. The light of the standard
Carcel lamp being 1, there was obtained with the Gagneau lamp with the
ordinary chimney 1.113 carcels, and with the Bayle chimney 1.404 carcels.
Thus 1.113:1.404 represents the ratio of the same lamp with the ordinary
chimney and with that of Bayle. Whence it follows that the light of the
lamp with the old chimney being 1, that with the new one is 1.26, say an
increase of about 25 per cent. There is nothing absolute about this
figure, however. On kerosene lamps the new chimney, compared with the
contracted Prussian one, gives an increase of 40 per cent. in illuminating
power, and the oil is burned without odor or smoke.
As it was of interest to see whether this increase in intensity was not
due to a greater consumption of oil, a determination was made of the
quantity of the latter consumed per hour. The Gagneau lamp, with the old
chimney, burned 62.25 grammes per hour, and with the Bayle 63 grammes in
the same length of time.
It may be concluded, then, that the increase in light is due to the
special form given the chimney. This new burner is applicable to gas lamps
as well as to oil and petroleum ones.
The effects obtained by the new chimney may be summed up as follows:
increase in illuminating power, as a natural result of a better
combustion; suppression of smoke; and a more active combustion, which
dries the carbon of the wick and thus facilitates the ascent of the oil.
The velocity of the current of air likewise facilitates the action of
capillarity by carrying the oil to the top of the wick. Moreover, the
great influx of air under the flame continually cools the base of the
chimney as well as the wick tube, and the result is that the excess of oil
falls limpid and unaltered into the reservoir, and produces none of those
gummy deposits that soil the external movements and clog up the conduits
through which the oil ascends. Finally, the influx of air produced by this
chimney permits of burning, without smoke and without charring the wick,
those oils of poor quality that are unfortunately too often met with in
commerce.--_La Nature._
* * * * *
MODERN LOCOMOTIVE PRACTICE.
[Footnote: Paper read before the Civil and Mechanical Engineers' Society,
April 2, 1884.]
By H. MICHELL WHITLEY, Assoc. M.I.C.E., F.G.S.
A little more than half a century ago, but yet at a period not so far
distant as to be beyond the remembrance of many still living, a
clear-headed North-countryman, on the banks of the Tyne, was working out,
in spite of all opposition, the great problem of adapting the steam engine
to railway locomotion. Buoyed up by an almost prophetic confidence in his
ultimate triumph over all obstacles, he continued to labor to complete an
invention which promised the grandest benefits to mankind. What was
thought of Stephenson and his schemes may be judged by the following
extracts from the _Quarterly Review_ of 1825, in which the introduction of
locomotive traction is condemned in the most pointed manner:
"As to those persons who speculate on making railways general throughout
the kingdom, and superseding every other mode of conveyance by land and
water, we deem them and their visionary schemes unworthy of notice.... The
gross exaggeration of the locomotive steam engine may delude for a time,
but must end in the mortification of all concerned.... It is certainly
some consolation to those who are to be whirled, at the rate of 18 or 20
miles per hour, by means of a high-pressure engine, to be told that they
are in no danger of being sea-sick while on shore, that they are not to be
scalded to death or drowned by the bursting of a boiler, and that they
need not mind being shot by the shattered fragments, or dashed in pieces
by the flying off or breaking of a wheel. But with all these assurances,
we would as soon expect the people of Woolwich to suffer themselves to be
fired off upon one of Congreve's ricochet rockets, as trust themselves to
the mercy of such a machine going at such a rate."
These words, strange and ludicrous as they seem to us, but tersely
expressed the general opinion of the day; but fortunately the clear head
and the undaunted will persevered, until success was at last attained, and
the magnificent railway system of the present, which has revolutionized
the world, is the issue. And the results are almost overwhelming in their
magnitude. Here, in Great Britain alone, 654,000,000 people travel
annually. There are 14,000 locomotives, and the rolling stock would form a
train nearly 2,000 miles long; while the number of miles traveled in a
year by trains is more than 10,000 times round the world; and the
passengers would form a procession 100 abreast, a yard apart, and 3,700
miles long.
These stupendous results have been attained gradually; if we go back to
1848, we find that on the London and Birmingham Railway the number of
trains in and out of Euston was forty-four per day. The average weight of
the engines was 18 tons, and the gross loads were, for passenger trains 76
tons, and for goods 160. Now, the weight of an express engine and tender
is about 65 tons, and gross loads of 250 to 300 tons for an express, and
500 tons for a coal train are not uncommon, while not only have the trains
materially increased in weight, owing to the carriage of third-class
passengers by all (except a few special) trains, and also to the lowering
of fares and consequent more frequent traveling, but the speed, and
therefore the duty of the engines, is greatly enhanced. A "Bradshaw's
Guide" of thirty-five years ago is now a rare book, but it is very
interesting to glance over its pages, and in doing so it will be found
that the fastest speed in all cases but one falls far short of that which
obtains at present. The following table will show what the alteration has
been:
_________________________________________________________________
| 1849. | 1884. |
|Speed miles|Speed miles|
| per hour. | per hour. |
-----------------------------------------+-----------+-----------+
Great Western--London to Didcot. | 56 | -- |
" " to Swindon. | -- | 53 |
North-Western--Euston to Wolverton. | 37 | -- |
" Northampton to Willesden. | -- | 511/2 |
South-Western--Waterloo to Farnborough. | 39 | -- |
" Yeovil to Exeter. | -- | 46 |
Brighton--London Bridge to Reigate. | 36 | -- |
" Victoria to Eastbourne. | -- | 45 |
Midland--Derby to Masborough. | 43 | -- |
" London to Kettering. | -- | 47 |
North-Eastern--York to Darlington. | 38 | -- |
" " | -- | 50 |
Great Eastern--London to Broxbourne. | 29 | -- |
" Lincoln to Spalding. | -- | 49 |
Great Northern--King's Cross to Grantham.| -- | 51 |
Cheshire Lines--Manchester to Liverpool. | -- | 51 |
-----------------------------------------+-----------+-----------+
With this problem then before them, increased weight, increased speed, and
increased duty, the locomotive superintendents of our various railways
have designed numerous types of engines, of which the author proposes to
give a brief account, confining himself entirely to English practice, as
foreign practice in addition would open too wide a field for a single
paper.
Commencing then with passenger engines for fast traffic, and taking first
in order the Great Western Railway, we find that it holds a unique
position, as its fast broad gauge trains are worked by the same type of
engine as that designed by Sir Daniel Grooch in 1848, although, of course,
the bulk of the stock has been rebuilt, almost on the same lines, and
rendered substantially new engines. They are single engines of 7 ft. gauge
with inside cylinders 18 in. diameter, and 24 in. stroke; the
driving-wheels are 8 ft. in diameter, and there are two pairs of leading
wheels, and one of trailing, all of 4 ft. 6 in. diameter. The total wheel
base is 18 ft. 6 in.; the boiler is 4 ft. 6 in. diameter, and 11 ft. 3 in.
long. The grate area is 21 square feet, and the heating surface is, in the
fire-box, 153 square feet; tubes, 1,800 square feet; total, 1,953 square
feet. The weight in full working order is, on the four leading wheels, 15
ton 18 cwt.; driving wheels, 16 tons; trailing wheels, 9 tons 10 cwt.;
total, 41 tons 8 cwt. The tender, which is low-sided and very graceful in
appearance, weighs 15 tons 10 cwt., and will hold 2,700 gallons of water.
The boiler pressure is 140 lb. on the square inch, and the tractive power
per pound of steam pressure in the cylinders is 81 lb. These engines take
the fast trains to the West of England; the Flying Dutchman averages 170
tons gross load, and runs at a mean time-table speed of 53 miles per hour,
which allowing for starting, stopping, and slowing down to 25 miles per
hour through Didcot gives a speed of nearly 60 miles an hour.
[Illustration: FIG. 1.--GREAT WESTERN RAILWAY.]
The average consumption of coal per mile, of thirteen of these engines,
with the express trains between London and Bristol, during the half-year
averaged 24.67 lb. per mile, the lowest being 23.22 lb., and the highest
26.17 lb., the average load being about eight coaches, or 243 tons. We
have already seen that in 1849 the Great Western express ran at a higher
rate than at present, being an exception to the general rule; and the
fastest journey on record was performed at this time by one of these
engines, when on May 14, 1848, the Great Britain took this Bristol
express, consisting of four coaches and a van, to Didcot, fifty-three
miles, in forty-seven minutes, or at the average speed of sixty-eight
miles an hour. The maximum running speed was seventy-five miles an hour,
and the indicated horse-power 1,000. A class of engines corresponding to
this type in their general dimensions, but with 7 ft. coupled wheels, was
introduced on the line, but it was not found successful. Through the
courtesy of Mr. Dean, I am enabled to give a table showing the running
speeds and loads of the principal express trains, broad and narrow gauge,
to the West and North of England, run on the Great Western Railway.
_Great Western Railway.--Average Speed and Weight of Express
Trains._
------------------+---------------------------+----------------------
| Speed to first stopping |
| station. | Weight of train.
+-------+--------+---------+-------+---------+-----
| | | Average | | |
Train. | | | speed-- |Engine |Carriages|
| | |miles per| and |and vans,|
|Station|Distance| hour. |tender.| empty. |Total
------------------+-------+--------+---------+-------+---------+-----
| | miles | | tons. | tons. |
BROAD GAUGE TO WEST OF ENGLAND: | | | |
9.0 Paddington to |Reading| 36 | 47 | 67 | 149 | 216
Plymouth | | | | | |
11.45 do. |Swindon| 771/4 | 53 | 67 | 104 | 171
| | | | | |
NARROW GAUGE TO THE NORTH| | | | |
10.0 Paddington to|Reading| 36 | 39.2 | 60 | 190 | 250
Birkenhead | | | | | |
4.45 do. |Oxford | 631/2 | 48.8 | 60 | 129 | 189
------------------+-------+--------+---------+-------+---------+-----
[Illustration: FIG 2.--GREAT WESTERN RAILWAY.]
The narrow gauge trains are worked by two classes of engines. The first is
a single engine with inside cylinders 18 in. diameter, 24 in. stroke. The
driving wheels are 7 ft. diameter, and the leading and trailing wheels 4
ft. The frames are double, giving outside bearings to the leading and
trailing axles, and outside and inside bearings to the driving axle; this
arrangement gives a very steady running engine, and insures, as far as can
possibly be done, safety in case of the fracture of a crank axle. The
frames are 15 inches deep, of BB Staffordshire iron. The wheel base is,
leading to driving wheels, 8 ft. 6 in; driving to trailing wheels, 9 ft.;
total, 17 ft. 6 in. The boiler is of Lowmoor iron, 10 ft. 6 in. long and 4
ft. 2 in. outside diameter. The grate area is 17 square feet, and the
heating surface is, tubes, 1,1451/2 square feet; fire-box 133 square feet;
total, 1,2781/2 square feet. The boiler pressure is 140 lb. on the square
inch, and the tractive power per lb. of mean pressure in cylinders, 92 lb.
The weight in full working order is, engine, leading wheel, 10 tons; ditto
driving wheels, 14 tons; ditto trailing wheels, 9 tons 10 cwt.; tender,
with 40 cwt. coal and 2,600 gals. water, 26 tons 10 cwt.; total, 60 tons.
These engines are extremely simple, but well proportioned, and are a very
handsome type, and their average consumption of coal, working trains
averaging ten coaches, is about 24.87 lb. per mile. The standard coupled
passenger express engine on the narrow gauge has inside cylinders 17 in.
diameter and 24 in. stroke; the coupled wheels are 6 ft. 6 in. diameter,
and the leading wheels 4 ft.; the wheel base is 16 ft. 9 in. The frames
are double, giving outside bearings to the leading axle, and inside
bearings to the coupled wheels. The boiler is 11 ft. long by 4 ft. 2 in.
diameter; the grate area is 16.25 square feet; and the heating surface is,
tubes, 1,216.5 square feet; fire-box, 97.0 square feet; total, 1,313.5
square feet. The boiler pressure is 140 lb., and the tractive power per
lb. of steam pressure in the cylinders, 88 lb. The weight in full working
order is on the leading wheels, 10 tons 5 cwt.; driving wheels, 11 tons;
trailing wheels, 9 tons 15 cwt.; total, 31 tons.
[Illustration: FIG. 3.--LONDON & NORTH-WESTERN RAILWAY.]
[Illustration: FIG. 4.--JOY'S VALVE GEAR.]
Turning now to the London and North-Western Railway, we find that between
1862 and 1865 the express trains were worked with a handsome type of
engines, known as the "Lady of the Lake" class. They have outside
cylinders 16 in. diameter and 24 in. stroke, with single driving wheels of
7 ft. 6 in. diameter, and leading and trailing wheels 3 ft. 6 in.
diameter, with a total wheel base of 15 ft. 5 in. The frames are single,
with inside bearings to all the wheels. The boiler is 11 ft. long and 4
ft. diameter, and the heating surface is in the tubes, 1,013 feet;
fire-box, 85 ft.; total, 1,098 feet. The tractive power per lb. of steam
pressure in the cylinders is 68 lb. The weight in full working order is on
the leading wheels, 9 tons 8 cwt.; driving wheels, 11 tons 10 cwt.;
trailing wheels, 6 tons 2 cwt.; total, 27 tons. The tender weighs 171/2 tons
in working order. These engines burn about 27 lb. of coal per mile with
trains of the gross weight of 117 tons, which is not at all an economical
duty. About 1872, the weight of the heavier express trains on the
North-Western had so increased, that a new standard type for this service
was designed, and is now the standard passenger engine; it has inside
cylinders 17 in. diameter and 24 in. stroke; the driving and trailing
wheels are coupled, and are 6 ft. 6 in. diameter, and the leading wheels 3
ft. 6 in. The frames of steel are single, with inside bearings to all the
wheels, and the boiler, of steel, is 9 ft. 10 in. long and 4 ft. 2 in.
diameter. The steel used has a tensile strength of 32 to 34 tons per
square inch, all the rivets are put in by hydraulic pressure, and the
magnetic oxide on the surface of the plates where they overlap is washed
off by a little weak sal-ammoniac and water. In testing, steam is first
got up to 30 lb. on the square inch, the boiler is then allowed to cool,
it is then proved to 200 lb. with hydraulic pressure, and afterward to 160
lb. with steam. The fire-box is of copper, fitted with a fire brick arch
for coal burning, and the grate area is 15 square feet. The heating
surface is, in the tubes, 1,013 square feet; fire-box, 89 square feet;
total, 1,102 square feet. The wheel base is 15 ft. 8 in., and the tractive
power 88 lb. for each lb. of steam pressure in the cylinders. These
engines, working the fast passenger trains at a speed of about 45 miles
per hour, burn about 35 lb. of coal per mile, when taking trains weighing
about 230 tons gross. A variation from this type has been adopted on the
Northern and Welsh sections, known as the "Precursor" class. These engines
have 5 ft. 6 in. coupled wheels, and weigh 31 tons 8 cwt. in working
order, but in other respects are very similar to the standard engines just
described; with the Scotch express, averaging in total weight 187 tons,
between Crewe and Carlisle, over heavy gradients, they burn 33 lb. of coal
per mile. These engines, although much more powerful than the standard
type, are not nearly of so handsome an appearance, the drivers seeming
much too small for the boiler under which they are placed. But by far the
boldest innovation on existing practice is the new class of compound
locomotives now being introduced by Mr. Webb. It is a six wheel engine,
with leading wheels 4 ft. diameter, and two pairs of drivers, 6 ft. 6 in.
diameter. The trailing drivers are driven by a pair of outside cylinders,
18 in. diameter and 24 in. stroke; and the leading drivers by a single
low-pressure cylinder--which takes the exhaust steam from the
high-pressure cylinders--of 26 in. diameter and 24 in. stroke, placed
under the center of the smoke-box. The boiler is the same as that in the
standard type of engine, but the wheel base is 17 ft. 7 in., and in order
to allow it to traverse curves easily, the front axle is fitted with a
radial axle-box, which is in one casting from journal to journal, and
fitted at each end with brass steps for the bearings; the box is radial,
struck from the center of the rigid wheel base, and the horn plates are
curved to suit the box, the lateral motion being controlled by strong
springs. Another peculiarity of this engine is that, instead of the
ordinary link motion, it is fitted with Joy's valve gear, which is now
being more and more adopted. This gear--which is of a most ingenious
decription--dispenses altogether with eccentrics, and so allows the inside
bearings to be much increased, those on these engines being 131/2 in. long;
and it is also claimed for it that it is simpler and less costly, weighs
less, and is more correct in its action than the ordinary link motion; the
friction is less, the working parts are simplified, it takes less oil,
and is well under the driver's eye. It also allows larger cylinders to be
got in between the frames of inside cylinder engines, as, the slide valves
may be placed on the top or bottom of the cylinders. This latter advantage
is a great one, as, with the ordinary link motion, large cylinders are
exceedingly difficult to design so as to get the requisite clear exhaust.
The action of the gear is as follows: A rod, a, is fixed by a pin at b, on
which it is free to turn, and is attached to a rod, c, at d, the other end
of which link is fastened to the connecting rod at e. At the point, f, in
this rod another lever, g, is connected to it, the upper end of which is
coupled to the valve rod, h, at i, and just below this point a second
connection is made to a block at j, sliding in a short curved piece, k.
The inclination of the block, k, governs the travel of the valve. The
total weight of the engine in working order is: On the leading wheels, 10
tons 8 cwt.; front drivers, 14 tons 4 cwt.; rear drivers, 13 tons 10 cwt.;
total, 37.75 tons. The tender weighs 25 tons in full working order. The
boiler pressure is 150 lb., and the usual point of cut-off in the high
pressure cylinders, when running at speed, is half-stroke, while the
pressure of steam admitted to the large cylinder is never to exceed 75 lb.
per square inch. The average consumption of coal between London and Crewe
is 26.6 lb. per train mile, or about 8 lb. per mile less than the standard
coupled engine. In an experiment made in October, 1883, one of these
engines took the Scotch express from Euston to Carlisle at an average
speed, between stations, of 44 miles an hour, the engine, tender, and
train weighing 230 tons, with a consumption of 291/2 lb. of coal per mile,
and an evaporation of 8.5 lb. of water per pound of fuel.
Mr. Webb's object, in designing this engine was to secure in the first
place a greater economy of fuel, and secondly, to do away with coupling
rods, while at the same time obtaining greater adhesion, with the freedom
of a single engine. The cost is much more than an ordinary locomotive, but
the saving in fuel is said to be 20 per cent. over the other engines of
the North Western Rail way. These engines run very sweetly, and are said
to steam freely, although with only half the usual number of blasts; but
from the small size of the high pressure cylinders, they are liable to
slip when starting heavy trains, as the low pressure cylinders are not
then effective, while the consumption of coal does not seem to show the
saving that would have been expected, when compared with ordinary engines
doing similar duty on other lines; for instance, the Great Northern single
engine takes trains of the same weight with the same consumption of coal
and at a somewhat higher speed. But it must, of course, be borne in mind
in making such a comparison, that the fuel used may not be of the same
quality.
Mr. Stirling, of the Great Northern, has adopted an entirely different
type of engine to those last described. Holding strongly that single
engines are more economical not only in running, but in repairs, and that
cylinder power is generally inadequate to the adhesion, he has designed
his magnificent well-known class of express engines. They have single
driving wheels 8 ft. in diameter, with a four-wheel bogie in front and a
pair of trailing wheels, 4 ft. diameter, behind. The frames are single,
and inside of one solid piece; the cylinders are outside 18 in. diameter
and 28 in. stroke; and the valve gear is of the usual shifting link
description. The boiler is of Yorkshire plates, 11 ft. 5 in. long and 4
ft. diameter, and the steam pressure is 140 lb.; while the tractive power
per lb. of steam in the cylinders is 94 lb. The fire-box is of copper, and
the roof is stayed to the outer shell by wrought iron radiating stays
screwed into both; a sloping mid-feather is placed in the fire-box.
[Illustration: FIG. 5.--GREAT NORTHERN RAILWAY.]
The tubes, 217 in number, are of brass, 1-9/16 in. diameter; and the
heating surface is in the tubes, 1,043 square feet; fire-box, 122 square
feet; total, 1,165 square feet. The fire-grate area is 17.6 square feet.
The wheel base from the center of the bogie pin to the trailing axle is 19
ft. 5 in., and the weight in working order is, on the bogie wheels, 15
tons; driving wheels, 15 tons; trailing wheels, 8 tons; total, 38 tons.
The tender weighs 27 tons. These engines are remarkable for their
efficiency; the traffic of the Great Northern Railway is exceedingly
heavy, and the trains run at a high rate, the average speed of the Flying
Scotchman being fifty miles an hour, and no train in the kingdom keeps
better time. "Those who remember this express at York in the icy winter of
1879-80, when the few travelers who did not remain thawing themselves at
the waiting-room fires used to stamp up and down a sawdusted platform,
under a darkened roof, while day after day the train came gliding in from
Grantham with couplings like wool, icicles pendent from the carriage
eaves, and an air of punctual unconcern; or those who have known some of
our other equally sterling trains--these will hardly mind if friendship
does let them drift into exaggeration when speaking of expresses." The
author well remembers how, when living some years ago at
Newcastle-on-Tyne, it was often his custom to stroll on the platform of
the Central Station to watch the arrival of the Flying Scotchman, and as
the hands of the station clock marked seven minutes past four he would
turn around, and in nine cases out of ten the express was gliding into the
station, punctual to the minute after its run of 272 miles. Such results
speak for themselves, and for the power of the engines employed, and one
of the best runs on record was that of the special train, drawn by one of
these locomotives, which in 1880 took the Lord Mayor of London, to
Scarborough. The train consisted of six Great Northern coaches, and ran
the 188 miles to York in 217 minutes, including a stop of ten minutes at
Grantham, or at the average rate of 541/2 miles an hour. The speed from
Grantham to York, 821/2 miles, with three slowing downs at Retford,
Doncaster, and Selby, averaged 57 miles an hour, and the 59 miles from
Claypole, near Newark, to Selby, were run in 601/2 minutes, and for 221/2
consecutive miles the speed was 64 miles an hour. In ordinary working
these engines convey trains of sixteen to twenty-six coaches from
King's-Cross with ease, and often twenty-eight are taken and time kept.
Considering that the Great Northern main line rises almost continuously to
Potter's Bar, 13 miles, with gradients varying from 1 in 105 to 1 in 200,
this is a very high duty, while, with regard to speed, they have run with
sixteen coaches for 15 miles at the rate of 75 miles an hour. Their
consumption of coal with trains averaging sixteen ten ton carriages is 27
lb. per mile, or 8 lb. per mile less than the standard coupled engine of
the North-Western with similar loads. Mr. Stirling's view, that the larger
the wheel the better the adhesion, seems borne out of these facts; thus to
take twenty-eight coaches, or a gross load of 345 tons, up 1 in 200 at a
speed of 35 miles an hour, would require an adhesive force of 8,970 lb.,
or 600 lb. per ton--more than a quarter the weight on the driving wheels.
These engines are magnificent samples of the most powerful express engines
of the present day.
The London, Brighton, and South Coast Railway Company has in the last few
years had its locomotive stock almost entirely replaced, and instead of
seventy-two different varieties of engines out of a total of 233, which
was the state of locomotive stock in 1871. a small number of
well-considered types, suited to the different class of work required, are
now in use. Mr. Stroudley considers--contrary to the opinion once almost
universally held--that engines with a high center of gravity are the
safest to traverse curves at high speed, as the centrifugal force throws
the greatest weight on the outer wheels, and prevents their mounting; also
that the greatest weight should be on the leading wheels, and that there
is no objection to these wheels being of a much larger diameter than that
usually adopted; in fact, by coupling the leading and driving wheels where
the main weight is placed a lighter load is thrown on the trailing wheels,
thus enabling them to traverse curves at a high speed with safety, while
it permits of a larger fire-box being used; and these principles have been
carried out in the newest class of engines, especially designed for
working the heavy fast passenger traffic of the line.
The modern express engines are of two types. The first is a single engine
with 6 ft. 6 in. driving wheels, and leading and trailing wheels 4 ft. 6
in. in diameter and a wheel base of 15 ft. 9 in. The frames are single,
with inside bearings to all the wheels; the cylinders are inside, 17 in.
diameter and 24 in. stroke. The boiler is 10 ft. 2 in. long and 4 ft. 3
in. diameter; the fire-box is of copper with a fire-grate area of 17.8
square feet, and the heating surface is in the tubes 1,080 square feet,
fire-box 102 square feet; total, 1182 square feet. The weight in working
order is about 35 tons. These engines have a tractive power of 89 lb. per
pound of mean steam pressure in the cylinders, and their consumption of
coal with trains averaging nine coaches is about 20 lb. per mile. The next
type of engine designed has coupled wheels under the barrel of the boiler
6 ft. 6 in. diameter, with cylinders 171/4 in. diameter and 26 in. stroke,
and were found so successful that Mr. Stroudley designed a more powerful
engine of the same class, especially to take the heaviest fast trains in
all weathers.
The 8:45 A.M. train from Brighton has grown to be one of the heaviest fast
trains in the kingdom, although the distance it runs is but very short,
while it is also exceptional in consisting entirely of first class
coaches, and the passengers mainly season ticket holders; it often weighs
in the gross 350 tons, and to take this weight at a mean speed of
forty-five to fifty miles an hour over gradients of 1 in 264 is no light
work.
[Illustration: FIG. 6.--LONDON, BRIGHTON, AND SOUTH COAST RAILWAY.]
The engines known as the "Gladstone" type have inside cylinders 181/4 in.
diameter and 26 in. stroke, with coupled wheels 6 ft. 6 in. diameter under
the barrel of the boiler; the trailing wheels are 4 ft. 6 in. diameter,
and the total wheel base is 15 ft. 7 in. The frames are inside, of steel 1
in. thick, with inside bearings to all the axles. The cylinders are cast
in one piece 2 ft. 1 in. apart, but in order to get them so close together
the valves are placed below the cylinders, the leading axle coming between
the piston and slide valve. The boiler is of iron, 10 ft. 2 in. long, and
4 ft. 6 in. diameter; and the heating surface is, in the tubes, 1,373
square feet; fire-box, 112 square feet; total, 1,485 square feet. The
grate area is 20.65 square feet, and the tractive power per pound of mean
cylinder pressure is 111 lb. The weight in full working order is--leading
wheels, 13 tons 16 cwt.; driving wheels, 14 tons 10 cwt.; trailing wheels,
10 tons 8 cwt.; total, 38 tons 14 cwt. The tender weighs 27 tons.
To enable these engines to traverse curves easily a special arrangement of
draw-bar is used, consisting of a T-piece with a wheel at each end working
in a curved path in the back of the frame under the foot plate; on the
back buffer beam a curved plate abuts against a rubbing piece on the
tender, through which the draw-bar is passed and screwed up against an
India-rubber washer, thus allowing the engine to move free of the tender
as the curvature of the road road requires; the flanges on the driving
wheel are also cut away, so as not to touch the rail. In order to reduce
the wear of the leading flanges, a jet of steam from the exhaust is
directed against the outer side of each wheel. The center line of the
boiler is 7 ft. 5 in. above the rails, and the tubes, of which there are
as many as 331, are bent upward 11/2 in., which permits expansion and
contraction to take place without starting the tubes, and they are stated
never to leak or give trouble. The feed-water is heated by a portion of
the exhaust steam and the exhaust from the Westinghouse brake, and the
boiler is consequently fed by pumps, is kept cleaner, and makes steam
better. The reversing gear is automatic and exceedingly ingenious, the
compressed air from the Westinghouse brake reservoir being employed to do
the heavy work. A cylinder 41/2 in. diameter is fitted with a piston and
rod attached to the nut of the reversing screw, and a three-way cock
supplies the compressed air behind the piston; this forces the engine into
back gear, and by allowing the air to escape, the weight of the valve
motion puts the engine in forward gear. There are no balance weights, and
the screw regulates the movement. There is also a very ingenious speed
indicator, which consists of a small brass case filled with water, in
which is a small fan driven by a cord from the driving wheel; a copper
pipe leads from the fan case to a glass gauge tube; the faster the fan
runs the higher the water will stand in the tube, thus indicating the
speed.
The author has been led to describe this engine fully on account of the
numerous ingenious appliances which have been adopted in its design. In a
trial trip on October 3, 1883, from Brighton to London Bridge and back,
with an average load of 191/2 coaches, or 285 tons gross, and with a speed
of 45 miles per hour, the consumption of coal was 31 lb. per train mile,
evaporating 8.45 lb. of water per pound of coal, and with as much as 1,100
indicated horse-power at one portion of the run. The finish and painting
of these engines is well considered, but the large coupled wheels give a
very high shouldered appearance, and as a type they are not nearly as
handsome as the single engines previously described.
From the Brighton to the South-Western Railway is but a step; but here a
totally different practice obtains to that adopted on most lines, all the
passenger engines having outside cylinders, where they are more exposed to
damage in case of accident, and, from being less protected, there is more
condensation of steam, while the width between the cylinders tends to make
an unsteady running engine at high speeds, unless the balancing is
perfect; but the costly crank axle, with its risk of fracture, is avoided,
and the center of gravity of the boiler may be consequently lowered, while
larger cylinders may be employed. On the other hand, inside cylinders are
well secured, protected, and kept hot in the smoke-box, thus minimizing
the condensation of steam. The steam ports are short, and the engine runs
steadier at high speeds, while with Joy's valve gear much larger cylinders
can be got in than with the link motion. Thus modern improvements have
minimized the advantages of the outside class.
The passenger engines for the fast traffic are of two types, the six-wheel
engines with 7 ft. coupled wheels, and the new bogie engines which are
being built to replace them. The former have 17 in. cylinders with 22 in.
stroke, and a pair of coupled wheels 7 ft. in diameter, the leading wheels
being 4 ft. diameter, and the wheel base 14 ft. 3 in. The grate area is
16.1 square feet, and the heating surface 1,141 square feet. The total
weight in working order is 33 tons. The chief peculiarity of this type of
engine consists in the boiler, which is fitted with a combustion chamber
stocked with perforated bricks, the tubes being only 5 ft. 4 in. long.
These engines are very expensive to build and maintain, owing to the
complicated character of the boiler and fire-box, but as a coal burning
engine there is no doubt the class was very efficient, but no more are
being built, and a new type has been substituted. This is an outside
cylinder bogie engine, with cylinders 181/2 in. diameter and 26 in. stroke;
the driving and trailing coupled wheels are 6 ft. 6 in. diameter, and the
bogie wheels 3 ft. 3 in. The wheel base to the center of the bogie pin is
18 ft. 6 in.; the heating surface is, in the tubes, 1,112; fire box, 104;
total, 1,216 sq. ft. The weight of the engine in working order is 42 tons.
[Illustration: FIG. 7.--MIDLAND RAILWAY.]
The Midland Railway route to the North is distinguished by the heavy
nature of its gradients; between Settle and Carlisle, running through the
Cumberland hills, attaining a height of 1,170 ft. above sea level, the
highest point of any express route in the kingdom; and to work heavy fast
traffic over such a line necessitates the employment of coupled engines.
The standard express locomotive of this company has inside cylinders 18
in. in diameter and 26 in. stroke. The coupled wheels are 6 ft. 9 in.
diameter, and the leading wheels 4 ft. 3 in., the total wheel base being
16 ft. 6 in., and the tractive force 104 lb. for each lb. of mean cylinder
pressure. The boiler is of best Yorkshire iron, 10 ft. 4 in. long and 4
ft. 1 in. diameter. The grate area is 17.5 square feet, and the heating
surface is, in the tubes, 1,096; fire-box, 110; total, 1,206. There are
double frames to give outside bearings to the leading axle, as in the
Great Western engine, and the engine is fitted with a steam brake. The
weight in full working order is--leading wheels, 12 tons 2 cwt.; driving
wheels, 15 tons; trailing wheels, 11 tons 6 cwt.; total, 38 tons 8 cwt.
The tender weighs 26 tons 2 cwt., and holds 3,300 gallons of water and 5
tons of coal. Latterly a fine type of bogie express engine has been
introduced, with inside cylinders 18 in. diameter and 26 in. stroke, and
four coupled driving wheels 7 ft. diameter. The total wheel base to the
center of the bogie pin is 18 ft. 6 in. The grate area is 17.5 square
feet, and the heating surface is, in tubes, 1,203 square feet, and
fire-box, 110; total, 1,313; and the engine weighs 42 tons in working
order. These engines take fourteen coaches, or a gross load of 222 tons,
at 50 miles an hour over gradients of 1 in 120 to 1 in 130, with a
consumption of 28 lb. of coal per mile. The London, Chatham, and Dover
Company has also some fine engines of a similar type. They have inside
cylinders 171/2 in. diameter and 26 in. stroke; the coupled wheels are 6 ft.
6 in. diameter, and the bogie wheels 3 ft. 6 in., the wheel base to the
center of the bogie pin being 18 ft. 2 in. The boiler is 10 ft. 2 in. long
and 4 ft. 2 in. diameter, the grate area is 16.3 square feet, and the
heating surface is, in the tubes, 962 square feet; fire-box, 107 square
feet; total, 1,069. The boiler pressure is 140 lb., and the tractive force
per lb. of steam in the cylinder 102 lb. The weight in full working order
is, on the bogie wheels, 15 tons 10 cwt.; driving wheels, 13 tons 10 cwt.;
trailing wheels, 13 tons; total, 42 tons.
Mr. Worsdell has lately designed for the Great Eastern Railway a fine type
of coupled express engine, which deserves mention. It has inside
cylinders 18 in. diameter and 24 in. stroke, with coupled wheels 7 ft.
diameter and leading wheels 4 ft. diameter, the latter being fitted with a
radial axle on a somewhat similar plan to that previously described as
adopted by Mr. Webb for the new North-Western engines; the frames are
single, with inside bearings to all the wheels, and Joy's valve gear is
used. The boiler pressure is 140 lb., and the tractive power per lb. of
mean cylinder pressure 92 lb. The total wheel base is 17 ft. 6 in. The
boiler, which is fed by two injectors, is of steel, 11 ft. 5 in. long and
4 ft. 2 in. diameter. The grate area is 17.3 square feet, and the heating
surface is, in the tubes, 1,083; fire-box, 117; total, 1,200 sq. ft. The
weight in working order is, on the leading wheels, 12 tons 19 cwt.;
driving wheels, 15 tons; trailing wheels, 13 tons 4 cwt.; total, 41 tons 3
cwt. These engines burn 27 lb. of coal per train mile with trains
averaging thirteen coaches. It has been seen that the Cheshire lines
express between Liverpool and Manchester is one of the fastest in England,
and the Manchester, Sheffield, and Lincolnshire Railway Company, who works
the trains, has just introduced a new class of engine specially for this
and other express trains on the line. The cylinders are outside, 171/2 in.
diameter and 26 in. stroke, with single driving wheels 7 ft. 5 in.
diameter, the leading and trailing wheels being 3 ft. 8 in. diameter. The
total wheel base is 15 ft. 9 in., and the frames are double, giving
outside bearings to the leading and trailing axles, and inside bearings to
the driving axle. The boiler is 11 ft. 6 in. long and 3 ft. 11 in.
diameter, and the grate area is 17 square feet. The heating surface is in
the tubes 1,057 square feet; fire-box, 87 square feet; total, 1,144 square
feet. The tractive force per pound of mean cylinder pressure is 88.4 lb.
The weight in full working order is, on the leading wheels, 11 tons 3
cwt.; driving wheels, 17 tons 11 cwt.; trailing wheels, 11 tons 18 cwt.;
total, 40 tons 12 cwt. This engine is remarkable for the great weight
thrown on the driving wheels, and its cylinder power is great in
proportion to its adhesion, thus allowing the steam to be worked at a high
rate of expansion, which is most favorable to the economical consumption
of fuel. There are numerous fine engines running on other lines, such as
the new bogie locomotives on the North-Eastern and Lancashire and
Yorkshire railways, and the coupled express engines on the Caledonian; but
those already described represent fairly the lending features of modern
practice, and the author will now notice briefly the two other classes of
engines--tank passenger engines for suburban and local traffic and goods
engines. The Brighton tank passenger engine is a good example of the
former class; it has inside cylinders 17 in. diameter and 24 in. stroke.
The two coupled wheels under the barrel of the boiler are 5 ft. 6 in.
diameter, and the trailing wheels 4 ft. 6 in.; there are single frames
with inside bearings to all the axles. The boiler pressure is 140 lb., and
the tractive force per pound of mean cylinder pressure 106 lb.; the total
wheel base is 14 ft. 6 in. The boiler is 10 ft. 2 in. long and 4 ft. 4 in.
diameter, and the heating surface is in the tubes, 858 square feet;
fire-box, 90 square feet; total, 948 square feet. The engine is furnished
with wing tanks holding 860 gallons of water, and carries 30 cwt. of coal.
The weight in working order is 38 tons. These engines have taken a maximum
load of twenty-five coaches between London and Brighton, but are mainly
employed in working the suburban and branch line traffic; their average
consumption of coal is 23.5 lb. per mile, with trains averaging about ten
coaches.
Another example is Mr. Webb's tank engine on the North-Western Railway,
which presents a contrast to the foregoing. It has inside cylinders 17 in.
diameter and 20 in. stroke, coupled wheels 4 ft. 6 in. diameter, and a
tractive power per lb. of mean cylinder pressure of 107 lb.; the wheel
base is 14 ft. 6 in. with a radial box to the leading axle; the heating
surface is in the tubes, 887; fire-box, 84; total, 971 square feet; the
weight in working order is 35 tons 15 cwt. The engine is fitted with
Webb's hydraulic brake, and steel, manufactured at Crewe, is largely used
in its construction. The consumption of coal-working fast passenger trains
has been 281/2 lb. per mile. There are many other types, such as the ten
wheel bogie tank engines of the London, Tilbury, and Southend and
South-Western railways; the saddle tank bogie engines, working the broad
gauge trains on the Great Western Railway, west of Newton; and the
familiar class working the Metropolitan and North London traffic. But the
same principle is adopted in nearly all--a flexible wheel base to enable
them to traverse sharp curves, small driving wheels coupled for adhesion,
and wing or saddle tanks to take the water. One notable exception is,
however, the little six wheel all-coupled engines weighing only 24 tons,
which work the South London traffic, burning 241/4 lb. of coal per mile,
with an average load of eleven coaches.
Goods engines on all lines do not vary much. As a rule they are six wheel
all-coupled engines, with generally 5 ft. wheels, and cylinders varying
between 17 in. and 18 in. diameter and 24 in. to 26 in. stroke; the grate
area is about 17 square feet, and the total heating surface from 1,000 to
1,200 sq. ft.; the average weight in full working order varies from 30 to
38 tons. One noteworthy exception occurs, however, on the Great Eastern
Railway, where a type of goods engine with a pony truck in front has been
introduced. The cylinders are outside 19 in. diameter and 26 in. stroke,
there are six coupled wheels 4 ft. 10 in. diameter, and the pony truck
wheels are 2 ft. 10 in. diameter; the total wheel wheel base is 23 ft. 2
in., but there are no flanges on the driving wheels. The boiler is 11 ft.
5 in. long and 4 ft. 5 in. diameter, the boiler pressure is 140 lb., and
the tractive force per lb. of mean cylinder pressure 162 lb.; the grate
area is 18.3 square feet, and the heating surface is in the tubes, 1,334
square feet; fire-box, 122 square feet; total, 1,456 square feet.
The weight in working order is on the pony truck, 8 tons 10 cwt.; leading
coupled, 12 tons 8 cwt.; driving coupled, 13 tons 5 cwt.; trailing
coupled, 12 tons 15 cwt.; total, 47 tons.
The tender weighs 28 tons in full working order. These engines take 40
loaded coal trucks or sixty empty ones, and burn 52 lb. of coal per train
mile, the worst gradient being 1 in 176. A notice of goods engines would
not be complete without alluding to a steep gradient locomotive, and a
good example is the engine which works the Redheugh Bank on the
North-Eastern Railway. This incline is 1,040 yards long, and rises for 570
yards 1 in 33, then for 260 yards 1 in 21.7, for 200 yards 1 in 25, and
finally for 110 yards 1 in 27. The engine, which is an all-coupled six
wheel tank engine, weighs 481/2 tons in working order, it has cylinders 18
in. diameter and 24 in. stroke, and 4 ft. wheels, the boiler pressure is
160 lb., and the tractive force per lb. of mean steam pressure in the
cylinders is 162 lb. This engine will take up the incline twenty-six coal
wagons, or a gross load of 218 tons, which is a very good duty indeed.
Having now passed in review the general types of engines adopted in modern
English practice, the author would briefly draw attention to some points
of design and some improvements effected in late years. And first, as to
the question of single or coupled engines, there is a great diversity of
opinion. Mr. Stirling conducts his traffic at a higher rate of speed, and
certainly with equal punctuality, with his magnificent single 8 ft.
engines, as Mr. Webb on the North-Western with coupled engines, and the
economy of fuel of the former class over the latter is very remarkable;
this is, no doubt, owing, as has been previously pointed out, to their
ample cylinder power, which permits of the steam being worked at a high
rate of expansion. There is no doubt that if single engines can take the
load they will do so more freely and at a less cost than coupled engines,
burning on the average 2 lb. of coal per mile less with similar trains.
With, regard to loads, it is a question whether any express train should
be made up with more than twenty-five coaches. The Great Northern engine
will take twenty-six and keep time, and the Brighton single engine has
taken the five P.M. express from London Bridge to Brighton, consisting of
twenty-two coaches, at a speed of forty-five miles per hour. Of course
where heavy gradients have to be surmounted, such as those on the Midland
route to Scotland, coupled engines are a necessity. Single engines are
said to slip more than coupled; thus an 8 ft. single Great Northern engine
running down the incline from Potter's Bar to Wood Green with twelve
coaches at the rate of sixty miles an hour was found to be making 242
revolutions per mile instead of 210; and in an experiment tried on the
Midland Railway it was found that a coupled engine with ten coaches at
fifty miles an hour made seventeen extra revolutions a mile, but when the
side rods were removed it made forty-three. The Great Western, Great
Northern, and Brighton mainly employ single engines for their fast
traffic; and the Manchester, Sheffield, and Lincolnshire have now adopted
the single type in preference to the coupled for their express trains;
while the North-Western, Midland, South-Western, and Chatham adopted the
coupled type. One noticeable feature in modern practice is the increased
height of the center line of boiler; formerly it was the great aim to keep
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