Scientific American Supplement, No. 492, June 6, 1885
by
Various
Part 2 out of 2
" 108 |5 " | 200,000 | 900 |222 " "
" 122 |5 " | 56,000 | 220 |254.5 " "
" 129[6]|5 " | 200,000 | 940 |212 " "
" 137 |5 " | 108,000 | 320 |337.5 " "
-----------------------------------------------------------------
[Footnote 6: Cells No. 23 and No. 129 are now in possession of Prof. W.
Gryllis Adams, of King's College, London; Dr. Werner Siemens has No. 25,
and Prof. George F. Barker, of Philadelphia, has No. 26.]
[Footnote 7: No. 24 was measured with a bridge multiplier of 6 to 1.]
Cells which are sensitive to light improve by being used daily, and their
sensitiveness becomes less if they are laid aside and not used for a
considerable length of time, especially if allowed to become overheated.
They should be kept cool, and exposed to light frequently, whether they
are used or not.
_Mode of measuring cells_.--So great is the sensitiveness of these cells
to external influences, that it is necessary to adopt some particular
system in measuring their resistance and to adhere strictly to that
system, as every change in the method of measurement produces a
difference in the result, and the different measurements would not be
comparable with each other. The reason for this will be explained
presently.
The system I have adopted is the Wheatstone's bridge arrangement, with
equal sides, never using multipliers except for some experimental
purpose. In each multiplier wire I have 500 ohms resistance. When the
bridge is balanced, one-half of the current flows through the cell and
acts upon the selenium. Between the bridge and the cell is a reversing
switch, so that the current can be reversed through the cell without
changing its course through the bridge. A Bradley tangent galvanometer is
used, employing the coil of 160 ohms resistance. The Leclanche battery is
exclusively used in measurements for comparison.
2. _The kind of battery employed_ has a marked effect upon the
sensitiveness to light, which is largely reduced or entirely destroyed
when the bichromate battery is used. The same cells again become
extremely sensitive with the Leclanche battery. We might expect that a
change in the current employed would cause a change in the _resistance_
of a cell, but it is not clear how or why it should affect the
_sensitiveness of selenium to light_.
"If one kind of battery current destroys its sensitiveness, may we not
suppose that another kind might increase its sensitiveness? Although the
Leclanche has operated well, some other may operate still better, and by
its special fitness for use on selenium cells may intensify their
actions, and so bring to light other properties yet unthought of. Is not
here a promising field for experiment, in testing the various forms of
battery already known, or even devising some new form especially adapted
to the needs and peculiarities of selenium cells?"
One year ago I made the foregoing suggestion in a paper on _A New Form of
Selenium Cell_, presented before this Association at Minneapolis. I am
now at liberty to state that my photo-electric battery, presently to be
described, marks an advance in the direction indicated. The current from
this battery increases the sensitiveness of the cells to light, and also
to reversal of current. One cell whose highest ratio in light was about
83 to 1, with the Leclanche battery, when measured with my battery gave a
ratio of 120 to 1. It seems to make the resistance of the cell both
higher in dark and lower in sunlight than with the Leclanche battery. But
the field is yet open to others, for the discovery of a battery which may
be still better for use with selenium cells.
3. _The two surfaces of the selenium act differently toward currents_
sent into them from the contiguous conductors. One surface offers a
higher resistance to the current than the other. The former I utilize as
the anode surface, as I have found that the cell is more sensitive to
light when the current enters at that surface, which is ordinarily the
one covered by the gold or other transparent conductor. Some cells have
this property but feebly developed; but in one instance the resistance
offered to the current by the anode surface was 256 times as high as that
offered by the cathode surface to the same current. In the majority of
cases, however, the ratio does not exceed ten times. Table B gives some
recent results.
TABLE B.
SENSITIVENESS TO REVERSAL OF DIRECTION OF CURRENT.
-----------------------+--------------+------------------+---------
| | Resistance |
No. of cell. | Battery. | "gold | "gold | Ratio
| | anode."|cathode."|
-----------------------+--------------+--------+---------+---------
| | ohms. | ohms. |
3/8 inch square. No. 4 | 5 elements. | 20,000 | 1,000 | 20 to 1
" " " 3 | Se. cell. | 6,500 | 400 | 16.2 "
Full size, No. 13 | 1 element. | 9,000 | 800 | 11.2 "
" " " 14 | 5 " | 2,440 | 130 | 18 "
" " " 15 | 5 " | 4,640 | 210 | 22 "
" " " 27 | 5 " | 6,900 | 440 | 16 "
" " " 126 | 1 " | 5,000 | 330 | 15 "
-----------------------+--------------+--------+---------+---------
The direction of the current is always indicated by stating the position
of the gold electrode, by the terms "gold anode" and "gold cathode." The
above measurements were made in dark.
4. _Sensitiveness to change of battery power_.--My cells are extremely
sensitive to any change in the strength or character of the current
flowing through them, which is shown by a corresponding change in the
resistance of the cell. I can, therefore, vary the resistance of one of
my cells in many ways, and the following may be specified--
(a) By changing the potential or electromotive force of the current
through the cell.
(b) By changing the "quantity" of the battery or current.
(c) By putting more or less resistance in the circuit.
(d) By dividing the current, by one or more branch circuits or shunts
around the cell.
(e) By varying the resistance in any or all of said circuits.
A cell whose resistance becomes greater as the battery power becomes
greater, and _vice versa_, I call an "L B cell" signifying _Like the
Battery power_. A "U B cell" is one whose resistance becomes greater as
the battery power (or strength of current) becomes less, and _vice
versa_, being _Unlike the Battery power_, or current strength.
These changes of resistance are not due to heating of the conductor or
the selenium, and the following instance will illustrate this. I have one
cell in which the selenium has about one-fourth inch square of surface
melted on a brass block one inch thick. This cell measured, with 25
elements of Leclanche, 40,000 ohms. On changing the battery to 5 elements
the resistance fell instantly to 30 ohms, and there remained. On again
using the current from 25 elements, the resistance instantly returned to
40,000 ohms. Had these results been due in any degree to heating, the
resistance would have changed gradually as the heat became communicated
to the brass, whereas no such change occurred, the resistances being
absolutely steady. Moreover, even the fusion of the selenium would not
produce any such change.
The "U B" property does not ordinarily change the resistance of the cell
to exceed ten times, i.e., the resistance with a weak current will not be
over ten times as high as with a strong one. But I have developed the "L
B" property to a far higher degree. Table C gives some recent results
obtained with L B cells, including one whose resistance, with 25 elements
Leclanche, was 11,381 times as high as with 8 elements, and which, after
standing steadily at 123 ohms (and then at 325 ohms with 1 element), on
receiving the current from 25 elements again returned to its previous
figure of 1,400,000 ohms.
TABLE C.
SENSITIVENESS TO CHANGE OF BATTERY POWER.
-----------------------+------------+------------+-------------
| Resistance | Resistance |
No. of cell. | with 25 | with 5 | Ratio of
| elements. | elements. | Change.
-----------------------+------------+------------+-------------
| ohms. | ohms. |
3/8 inch square, No. 1 | 40,000 | 30 | 1,333 to 1
3/8 " " " 2 | 13,000 | 40 | 325 "
1/4 " " " 1 | 1,400,000 | 123[8] | 11,381 "
1/2 " " " 2 | 500,000 | 62 | 8,064 "
1/2 " " " 5 | 3,500 | 21 | 167 "
Full size, No. 81 | 68,000 | 121 | 561 "
" " " 82 | 9,000 | 64 | 140 "
" " " 83 | 17,300 | 74 | 233 "
" " " 119 | 35,600 | 19 | 1,894 "
-----------------------+------------+------------+-------------
[Footnote 8: This measurement was obtained with 8 elements.]
The results in the table were obtained by changing the strength of
current by throwing in more or less of the battery. Like results can be
obtained by varying the current through the cell by any of the other
methods before specified. The above measurements were in dark.
5. _Dual state of selenium_.--My cells, when first made seem to have two
states or conditions. In one, their resistance is very low, in the other
it is high. When in the low state they are usually not very sensitive, in
any respect. I therefore raise the resistance, by sending an intermittent
or an alternating current though the cells, and in their new condition
they at once become extremely sensitive to light, currents, and other
influences. In some cases they drop to the low state again, and require
to be again brought up, until, after a number of such treatments, they
remain in the sensitive state. Occasionally a cell will persist in
remaining in the insensitive state. The before mentioned treatment raises
it up for a moment, but, before the bridge can be balanced and the
resistance measured, it again drops into the low or insensitive state.
Some cells have been thus stimulated into the high or sensitive state
repeatedly, and every means used to make them stay there, but without
avail; and they have had to be laid aside as intractable.
In the earlier stages of my investigations, before the discovery of this
dual state and the method of changing a cell from the insensitive to the
sensitive condition, hundreds of cells were made, finished, and tested,
only to be then ruthlessly destroyed and melted over, under the
impression that they were worthless. Now, I consider nothing worthless,
but expect sooner or later to make every cell useful for one purpose or
another.
The most singular part of this phenomenon is the wide difference in the
resistance of the cells in the two states. In the low state, it may be a
few ohms, or even a few hundredths of an ohm. In the high state, it is
the normal working resistance of the cell, usually between 5,000 and
200,000 ohms, but is often up among the millions. The spectacle of a
little selenium being stimulated, by a few interruptions of the current
through it, into changing its resistance from a fraction of an ohm up to
a million or several millions of ohms, and repeatedly and instantly
changing back and forth, up and down, through such a wide range, we might
almost say changing from zero to infinity, and the reverse, instantly, is
one which suggests some very far-reaching inquiries to the electrician
and the physicist. What is the nature of electrical conductivity or
resistance, and how is it so greatly and so suddenly changed?
6. _Radio-electric current generators_.--My cells can be so treated that
will generate a current by simple exposure to light or heat. The light,
for instance, passes through the gold and acts upon its junction with
the selenium, developing an electromotive force which results in a
current proceeding from the metal back, through the external circuit, to
the gold in front, thus forming a photo-electric dry pile or battery. It
should preferably be protected from overheating, by an alum water cell or
other well known means.
The current thus produced is radiant energy converted into electrical
energy directly and without chemical action, and flowing in the same
direction as the original radiant energy, which thus continues its
course, but through a new conducting medium suited to its present form.
This current is continuous, constant, and of considerable electromotive
force. A number of cells can be arranged in multiple arc or in series,
like any other battery. The current appears instantly when the light is
thrown upon the cell, and ceases instantly when the light is shut off. If
the light is varied properly, by any suitable means, a telephonic or
other corresponding current is produced, which can be utilized by any
suitable apparatus, thus requiring no battery but the selenium cell
itself. The strength of the current varies with the amount of light on
the cell, and with the extent of the surface which is lighted.
I produce current not only by exposure to sunlight, but also to dim
diffused daylight, to moonlight, and even to lamplight. I use this
current for actual working purposes, among others, for measuring the
resistance of other selenium cells, with the usual Wheatstone's bridge
arrangement, and for telephonic and similar purposes. Its use for
photometric purposes and in current regulators will be mentioned further
on. It is undoubtedly available for all uses for which other battery
currents are employed, and I regard it as the most constant, convenient,
lasting, readily used, and easily managed pile or battery of which I have
any knowledge. On the commercial scale, it could be produced very
cheaply, and its use is attended by no expense, inasmuch as no liquids or
chemicals are used, the whole cell being of solid metal with a glass in
front, for protection against moisture and dust. It can be transported or
carried around as easily and safely as an electro-magnet, and as easily
connected in a circuit for use wherever required. The current, if not
wanted immediately, can either be "stored" where produced, in storage
batteries of improved construction devised by me, or transmitted over
suitable conductors to a distance, and there used, or stored as usual
till required.
7. _Singing and speaking cells_.--When a current of electricity flowing
through one of my selenium cells is rapidly interrupted, a sound is given
out by the cell, and that sound is the tone having the same number of air
vibrations per second as the number of interruptions in the current. The
strength of the sound appears to be independent of the direction of the
current through the cell. It is produced on the face of the cell, no
sound being audible from the back of the cell. An alternating current
also produces a sound corresponding to the number of changes of
direction. Experiments also show that, if a telephonically undulating
current is passed through the cell, it will give out the speech or other
sound corresponding to the undulations of the current--and, furthermore,
that the cell will sing or speak in like manner, without the use of a
current, if a suitably varied light is thrown upon it while in closed
circuit.
My experiments having been devoted especially to those branches of the
subject which promised to be more immediately practically valuable, I
have not pursued this inquiry very far, and offer it for your
consideration as being not only interesting, but possibly worthy of full
investigation.
GENERAL OBSERVATIONS ON THE PROPERTIES OF CELLS.
From the number of different properties possessed by my cells, it might
be anticipated that the different combinations of those properties would
result in cells having every variety of action. This is found to be the
case. As a general rule, the cells are noteworthy in one respect only.
Thus, if a cell is extremely sensitive to light, it may not be specially
remarkable in other respects. As a matter of fact, however, the cells
most sensitive to the light are also "U B cells."
The property of sensitiveness to light is independent of the power to
generate current by exposure to light--the best current-generating cells
being only very moderately sensitive to light, and some of the most
sensitive cells generate scarcely any current at all. Current-generating
cells are, almost without exception, "U B cells;" and the best
current-generating cells are strongly polarized, showing a considerable
change of resistance by reversing the direction of a current through
them; and they are also strong "anode cells," i.e., the surface next to
the gold offers a higher resistance to a battery current than the other
surface of the selenium does. The power to generate a current is
temporarily weakened by sending a battery current through the cell while
exposed to light, in either direction. The current generated by exposure
to light is also weakened by warming the cell, unless the cell is
arranged for producing current by exposure to heat.
The properties of sensitiveness to light and to change of battery power
are independent of each other, as I have cells which are sensitive to
change of current but absolutely insensitive to light--their resistance
remaining exactly the same whether the cells are in darkness or in
sunlight. I also have cells which are sensitive to light, but are
unaffected by change of battery power, or by reversing the direction of
the current through them.
The sensitiveness to change of battery power is also independent of the
sensitiveness to reversal of direction of the current. Among the best "L
B cells," some are "anode cells" and others are "cathode cells," while
still others are absolutely insensitive to reversal of current or to the
action of light.
_Constancy of the resistance_.--A noticeable point in my cells is the
remarkable constancy of the resistance in sunlight. Allowing for
differences in the temperature, the currents, and the light, at different
times, the resistance of a cell in sunlight will remain practically
constant during months of use and experiments, although during that time
the treatments received may have varied the resistance in dark hundreds
of thousands of ohms--sometimes carrying it up, and at others carrying it
down again, perhaps scores of times, until it is "matured," or reaches
the condition in which its resistance becomes constant.
As has already been stated, the sensitiveness of a cell to light is
increased by proper usage. This increased sensitiveness is shown, not by
a lowered resistance in light, but by an increased resistance in dark.
This change in the cells goes on, more or less rapidly, according as it
is retarded or favored by the treatment it receives, until a maximum is
reached, after which the resistance remains practically constant in both
light and dark, and the cell is then "matured," or finished. The
resistance in dark may now be 50 or even 100 times as high as when the
cell was first made, yet, whenever exposed to sunlight it promptly shows
the same resistance that it did in the beginning. The various treatments,
and even accidents, through which it has passed in the mean time, seem
not to have stirred its molecular arrangement under the action of light,
but to have expended their forces in modifying the positions which the
molecules must normally assume in darkness.
_Practical applications_.--There are many peculiarities of action
occasionally found, and the causes of such actions are not always
discernible. In practice, I have been accustomed to find the
peculiarities and weaknesses of each cell by trial, developing its
strongest properties and avoiding its weaknesses, until, when the cell is
finished, it has a definite and known character, and is fitted for
certain uses and a certain line of treatment, which should not be
departed from, as it will be at the risk of temporarily disabling it. In
consequence of the time and labor expended in making cells, in the small
way, testing, repairing damages done during experiments, etc., the cost
of the cells now is unavoidably rather high. But if made in a commercial
way, all this would be reduced to a system, and the cost would be small.
I may say here that I do not make cells for sale.
The applications or uses for these cells are almost innumerable,
embracing every branch of electrical science, especially telegraphy,
telephony, and electric lighting, but I refrain from naming them. I may
be permitted, however, to lay before you two applications, because they
are of such general scientific interest. The first is my
_Photometer_.--The light to be measured is caused to shine upon a
photo-electric current-generating cell, and the current thus produced
flows through a galvano-metric coil in circuit, whose index indicates
upon its scale the intensity of the light. The scale may be calibrated by
means of standard candles, and the deflections of the index will then
give absolute readings showing the candle power of the light being
tested. Or, the current produced by that light and that produced by the
standard candle may be compared, according to any of the known ways of
arranging and comparing different lights--the cell being lastly exposed
alternately to the two lights, to see if the index gives exactly the same
deflection with each light.
This arrangement leaves untouched the old difficulty in photometry, that
arising from the different _colors_ of different lights. I propose to
obviate that difficulty in the following manner. As is well known, gold
transmits the green rays, silver the blue rays, and so on; therefore, a
cell faced with gold will be acted upon by the green rays, one faced with
silver by the blue rays, etc. Now, if we construct three cells (or any
other number), so faced that the three, collectively, will be acted upon
by all the colors, and arrange them around the light to be tested, at
equal distances therefrom, each cell will produce a current corresponding
to the colored rays suited to it, and all together will produce a current
corresponding to all the rays emitted by the light, no matter what the
proportions of the different colors may be. The three currents may act
upon the same index, but each should have its own coil, not only for the
sake of being able to join or to isolate their influences upon the index,
but also to avoid the resistances of the other cells. If a solid
transparent conductor of electricity could be found which could be thick
enough for practical use and yet would transmit all the rays perfectly,
i.e., transmit white light unchanged, that would be still better. I have
not yet found a satisfactory conductor of that kind, but I think the plan
stated will answer the same purpose. This portion of my system I have not
practically tested, but it appears to me to give good promise of removing
the color stumbling-block, which has so long defied all efforts to remove
it, and I therefore offer it for your consideration.
_Photo-electric regulator_.--My regulator consists of a
current-generating cell arranged in front of a light, say an electric
lamp, whose light represents the varying strength of the current which
supports it. The current produced in the cell by this light flows through
an electro-magnetic apparatus by means of which mechanical movement is
produced, and this motion is utilized for changing resistances, actuating
a valve, rotating brushes, moving switches, levers, or other devices.
This has been constructed on a small scale, and operates well, and I
think it is destined to be largely used, as a most sensitive, simple, and
perfect regulator for currents, lights, dynamos, motors, etc., etc.,
whether large or small.
In conclusion, I would say that the investigation of the physical
properties of selenium still offers a rare opportunity for making very
important discoveries. But candor compels me to add that whoever
undertakes the work will find it neither an easy nor a short one. My own
experience would enable me to describe to you scores of curious
experiments and still more curious and suggestive results, but lack of
time prevents my giving more than this very incomplete outline of my
discoveries.
* * * * *
ELECTRICITY APPLIED TO THE MANUFACTURE OF VARNISH.
Messrs. Muethel & Luetche, of Berlin, recommend the following process for
the manufacture of varnish: The oils are treated by gases or gaseous
mixtures that have previously been submitted to the action of electric
discharges. The strongly oxidized oxygenated compounds that are formed
under such circumstances give rise, at a proper elevation of temperature,
to compounds less rich in oxygen, and the oxygen that is set free acts
upon the fatty acid that it is proposed to treat. A mixture of equal
parts of chlorine and steam may be very advantageously employed, as well
as anhydrous sulphuric acid and water, or oxygen, anhydrous sulphuric
acid and protoxide of nitrogen, nitrogen, oxygen, and hydrogen, protoxide
of nitrogen and air, or oxygen, and so on.
The apparatus is shown in section in the accompanying engraving; a is a
steam-pipe running from the boiler to the motor. From this pipe branch
conduits, b, that enter the vessels, B, in which the treatment is
effected, and that run spirally through the oil. At the lower part of the
vessel, B, there is tube wound into a flat spiral, and containing a large
number of exceedingly small apertures.
The oxidizing apparatus is shown at p. The gaseous mixture enters through
the tube, n, traverses the apparatus, p, and enters the vessel, B,
through the tubes, g and D. Fig. 2 gives the details of the oxidizing
apparatus, which consists of two concentric glass tubes, A and F,
soldered at x. A is closed beneath and held in a cylinder, C; F contains
a small aperture through which passes a tube, E. The gaseous mixture
enters through the latter, traverses the annular space between the tubes,
A and F, and then makes its exit through H, whence it goes to a similar
apparatus placed alongside of the other. The shaded parts of the
engraving represent bodies that are good conductors of electricity and
that communicate with the two poles of any electrice source whatever.
[Illustration: FIGS. 1 AND 2.]
The operation is as follows: After opening the tube, e, linseed oil is
introduced into the vessel, B, until the latter is half full, and, after
this, e is closed and the worm, S, is allowed to raise the temperature to
between 60 deg. and 80 deg.. Then the cock of the tube, d, which communicates
with an air pump, is opened, and the pressure is diminished to about 730
mm. of mercury. At this moment the oxidizing apparatus are put in
communication with an induction bobbin that is interposed in the circuit
of a dynamo, while through the tube, n, there is made to enter a mixture
of equal parts (in volume) of sulphurous acid, oxygen, and air. At the
same time, the cock of the tube, g, is opened, while the stirrer, T, is
set in motion. In this way we obtain, in a much shorter time than by
ordinary processes, a very liquid, transparent varnish, which, when
exposed to the air, quickly hardens. It is possible, with the same
process, to employ a mixture (in volumes) of two parts of protoxide of
nitrogen with one and a half parts of atmospheric air, or even protoxide
of nitrogen alone.
When it is judged that the operation is finished, the tube, g, is opened,
the stirrer is stopped, and the tube, c, is opened after d has been
closed. The steam then forces the varnish to pass through the tube, f,
and traverse the washing apparatus, which is filled half full of water,
that is slightly ammoniacal, and is heated by a circulation of steam, S.
Finally, the product, washed and free from every trace of acid is
collected upon making its exit from the tube, h.--_La Lumiere
Electrique._
* * * * *
NAGLO BROTHERS' TELEPHONE SYSTEM.
We borrow from the _Elektrotechnische Zeitung_ the following details in
regard to the telephonic installations made by the Brothers Naglo at
Berlin. Fig. 1 gives the general arrangement of a station, where J is an
inductor set in motion through a winch, K, and a pair of friction
rollers; W, a polarized call; U, an ordinary two-direction commutator; B,
a lightning protector; and L and T, the two terminals of the apparatus,
one of them connecting with the line and the other with the earth. The
interesting point of this system is the automatic communication which
occurs when the inductor, J, is moved. At the same moment that the winch,
K, is being moved, the disk, P, is carried from right to left and brought
into contact with the spring, f_{2}. As soon as the winch is left to
itself a counter-spring forces the disk, P, to return to a contact with
the spring, f_{1}. Figs. 2 and 3 show the details of such communication.
The winch, K, is keyed to one of the extremities of a sleeve that carries
the disk, P, at its other extremity. This sleeve is fixed upon the axle
of the first friction roller, that is to say, upon the axle that controls
the motion of the inductor, and is provided at the center with two
helicoidal grooves, e, at right angles with one another. In these grooves
slides a tappet, n, connected with the axle.
[Illustration: FIG. 1.]
Under the influence of the counter-spring at the left of the disk, P, the
latter constantly tends to occupy the position shown in Fig. 2, which is
that of rest. As soon as the winch, K, is revolved, whatever be the
direction of the motion, the axle can only be carried along when the
tappet, n, has come to occupy the position shown in Fig. 3, that is to
say, when the disk has moved from right to left a distance corresponding
to the fraction of the helix formed in the sleeve.
This stated, it is easy to understand the travel of the currents. Fig. 1
shows the station at rest. The current that arrives through L passes
through the lightning protector, the body of the commutator, U, the
terminal, v, and the call, W, bifurcates at P, and is closed by the
earth. The inductor is in circuit, but, as it is in derivation, upon a
very feeble resistance, v, nearly the whole of the current passes through
the latter. When it is the station that is calling, the call, W, is put
in derivation upon the circuit, f_{2} p, h, so that the portion of the
circuit that passes through q W v is exceedingly feeble, and incapable of
operating the bell of the post that is calling.
[Illustration: FIGS. 2 AND 3.]
Finally, when the telephone is unhooked, the inductor, J, and the bell,
W, are thrown out of circuit, and the telephone is interposed between d
and i, that is, between L and T.--_La Lumiere Electrique_.
* * * * *
THE GERARD ELECTRIC LAMP.
In the Gerard incandescent lamp the carbons have the form of a V. They
are obtained by agglomerating very finely powdered carbon, and passing it
through a draw plate. At their extremity they are cemented together with
a small quantity of carbon paste, and their connection with the platinum
conducting wires is effected by means of a cylinder of the same paste
surmounted by a cone. These couplings secure a good contact, and, by
their dimensions, prevent the attachments from becoming hot and
consequently injuring the carbon at this point. The cone forms a
connection of decreasing section, and prevents the carbon from getting
broken during carriage.
This process of manufacture permits of obtaining lamps of all
intensities, from 3 candles up. The following, according to Mr. Gerard,
are the consumptions of energy in each size of lamp:
Candles. Volts. Amperes.
No. 0. 10 16 1.5
" 1. 25 25 2
" 2. 50 30 2.5
[Illustration: GERARD'S INCANDESCENT LAMP.]
It will be seen that these lamps require a relatively intense current
with much less fall of potential than the Swan, for example--this being
due to the diameter of the filament. But, what is an inconvenience as
regards mounting, if we wish to supply them by ordinary machines (for
they must be mounted in series of 3 on each derived circuit if the
machine gives, as most frequently the case, 100 volts), is an advantage
as regards the quality and steadiness of the light and the duration of
the lamps.
The part in which the energy is expended is homogeneous, as might be
supposed from the mode of manufacture, and as may be ascertained from a
microscopical examination, and it is exempt from those variations in
composition that are found in carbons of a vegetable nature, like the
Edison. Besides, being of relatively large diameter, the lamp is capable
of supporting a very great increase of temperature.
The process employed for fixing the lamps is as simple as can be. Each
platinum wire is soldered to a piece of copper that surrounds the base of
the lamp and that is fixed to the glass with a special cement. These two
armatures intertwine, but at a sufficient distance apart to prevent
contact. They carry a longitudinal projection and an inflation that fit
by hard friction into two copper springs connected electrically with the
circuit. It is only necessary to lift the lamp in order to remove it from
the support; and the contrary operation is just as easy.--_Le Genie
Civil_.
* * * * *
A NEW REFLECTING GALVANOMETER.
Fig. 1 shows an elevation of the instrument and a horizontal section of
the bobbins. Two pairs of bobbins, cc, cc, are so arranged that the axes
of each pair are parallel and in the same vertical plane. Each pair is
supported by a vertical brass plate, and the two plates make an angle of
about 106 deg. with each other, so that the planes containing the axes of the
bobbins make an angle of about 74 deg.. Two horseshoe magnets, m m, made of
1/25 inch steel wire, are connected by a very light piece of aluminum and
placed at such a distance from each other that, on being suspended, the
two branches of each of the magnets shall freely enter the respective
bores of the two bobbins fixed upon the same plate, and, when the whole
system is in equilibrium and the bobbins free from current, the two
branches of each of the magnets shall nearly coincide with the axes of
such bores. The magnets are not plane, but are curved so as to form
portions of a vertical cylinder whose axis coincides with the direction
of the suspension wire, and to which the axes of the bobbins are tangent
at their center, approximately to the points where the poles of the
magnets are situated.
[Illustration: FIG. 1. GRAY'S GALVANOMETER.]
The needles have been given this form so that their extremities shall not
touch the sides of the bore during considerable deflections.
In the instrument which the inventors, Messrs. T. & A. Gray, used in
their experiments upon the resistance of glass, the needles were arranged
so that their poles of contrary name were opposite.
[Illustration: FIG. 2.]
The system of needles is suspended from the extremity of a screw, p,
which passes into a nut, n, movable between two stationary pieces. On
revolving the nut, we cause the screw to rise or lower, along with the
entire suspended part, without twisting the thread.
The four bobbins are grouped for tension, and have a total resistance of
30,220 ohms. They contain 16,000 feet of No. 50 copper wire, forming
62,939 revolutions, nearly equally divided between the four bobbins. When
a current is passing through the bobbins, the poles of one of the
horseshoe magnets are attracted toward the interior of the corresponding
bobbins, while those of the other are repelled toward the exterior by the
two other bobbins. We thus have a couple which tends to cause the system
to revolve around the suspension axis. A mirror, which is fixed upon a
vertical piece of aluminum, a, gives, in the usual manner, a reflected
image upon a scale, thus allowing the deflections to be read. A
compensating magnet, M, is supported by a vertical column fixed to the
case, above the needles. This magnet may be placed in the different
azimuths by means of a tangential screw, t. The extremities of the bobbin
wires are connected with three terminals, T, T', T squared, and the
instrument may, by a proper arrangement, became differential. These
terminals, as well as the communicating wires, are insulated with
ebonite.
Thus arranged, the instrument is capable of making a deflection of one
division of 1/50 inch upon a scale placed at a distance of a little more
than a yard, with the current produced by one daniell of 10 ohms. This is
a degree of sensitiveness that cannot be obtained with any of the astatic
instruments known up to the present. By regulating the needles properly,
a greater degree of sensitiveness may be attained, but then the duration
of the needles' oscillation becomes too great. The sensitiveness of the
instrument is sufficiently great to allow it to be used in many cases,
even with a moderate duration of oscillation.
In their experiments upon the resistance of glass, the inventors employed
an instrument that was not arranged for giving great sensitiveness, and
one with which resistances of from 10^{4} to 10^{5} megohms could be
measured by the use of a pile of 120 daniells.
The instrument can be given another form. The four bobbins may be
arranged symmetrically in the same plane, and the two horseshoe magnets
be supported by an S-shaped aluminum bar. The latter traverses the plate
that supports the bobbins, in such a way that one of the magnets enters
one of the bobbins that correspond to it on one side of the plate, and
the other on the other side, as shown in Fig. 2. The bobbins are so
connected that, when they are traversed by a current, both magnets are at
the same time attracted toward the interior or repelled toward the
exterior of the bobbins. Such a form of the instrument has the advantage
of being more easily constructed, while the regulation of the magnets
with respect to the bore of the bobbins is easier.
The chief advantage of the instrument results from the fact that, owing
to the arrangement of the magnets and bobbins, a large portion of the
wires of the latter is situated very near the poles of the magnets, and
in a position very favorable for electro-magnetic action. The instrument
presents no difficulties as regards construction, and costs no more than
an ordinary one.
We might even arrange a single horseshoe magnet, or an S-shaped one,
horizontally, and employ but a single pair of bobbins, and thus have a
non-astatic apparatus based upon the same principle. But in astatic
instruments it is better to place the magnets in such a way that the two
branches shall be in the same vertical plane.
Were the line that joins the two poles vertical, the system would be
perfectly astatic in a uniform field, since each magnet in particular
would then be perfectly astatic. A pair of horseshoe magnets may thus be
regulated in such a way as to form a perfectly astatic system in a
uniform field and to preserve an almost invariable zero, this being
something that it is very difficult to obtain with the ordinary
arrangement of needles, especially when a compensating magnet is used;
for, in such a case, one of the needles becomes more or less magnetized,
while the other becomes demagnetized, according to the position of the
compensating magnet.--_La Lumiere Electrique_.
* * * * *
HISTOLOGICAL METHODS.
A cat, dog, rabbit, or Guinea pig will furnish parts from which sections
can be cut for the study of histology. Whichever animal is selected
should be young and well developed. Put it under influence of chloroform,
and open into the cavity of the chest; make an incision into the right
ventricle, and allow the animal to bleed to death; cut the trachea and
inject the lungs with a solution of one and a half drachms of chromic
acid in one quart of water, care being taken not to overdistend the lung.
Tie the severed end to prevent the escape of the fluid, and carefully
remove the lung. It is a difficult thing to do this without rupturing it,
but with care and patience it can be done. Place the lungs in a solution
of the same strength as used for injecting; after fifteen or twenty hours
change it to a fresh solution, and allow it to remain for about a month,
and then change it to rectified spirits, in which it may remain until
required.
Cut the tongue into several transverse and longitudinal pieces, also the
small intestines, and put them into a solution of fifteen and one-half
grains chromic acid, thirty grammes bichromate of potash, and three pints
of water; change the solution the next day, and let them remain two weeks
and then place in spirits. Cut longitudinal and transverse portions of
the stomach and large intestines, wash in a weak solution of salt and
water, and put them in the same solution as used for the lungs, and treat
similarly.
Cut the kidneys longitudinally and transversely, and put them in a
solution of six and one-half drachms bichromate of potash, two and
one-half drachms sodium sulphate, one quart of water; change the solution
the next day, and at the end of four weeks transfer to alcohol. Wash the
inner surface of the bladder with salt and water, and after cutting it
longitudinally and transversely, put the sections in a solution of three
drachms bichromate of potash in a quart of water. Cut the liver into
small parts, and place in the same solution as used for the kidneys;
change the solution after a day, and let them remain four or five weeks,
then change to spirits. The spleen and portions of the thin abdominal
muscles may be placed in a solution of three drachms chromic acid to one
quart of water, and transferred to alcohol after three or four weeks.
Carefully remove an eye and divide it behind the crystalline lens, put
the posterior portion in a solution made by dissolving fifteen grs.
chromic acid in five drachms water, and slowly adding five and one-half
ounces alcohol; change to spirits in two weeks. The lens should be put in
the same solution, but should remain a few days longer. Open the head,
remove the brain, and place transverse and longitudinal sections of it
in spirits for eighteen hours, then transfer to a solution of one drachm
chromic acid in a quart of water, and let it remain until hard enough to
cut. Place the uterus in a solution of one and one-half drachms chromic
acid in one quart of water, change to a new solution the next day, and at
the end of a month transfer to alcohol.
The bones from one of the legs should be carefully cleaned of its
muscles, cut into several pieces, and placed in a solution of fifteen and
one-half grains chromic acid, one-half drachm nitric acid, and six ounces
water. Change the fluid frequently until the bones are sufficiently
softened, and then change to alcohol.
_Section cutting_ machines for cutting sections can be procured of the
dealers, but a very simple and effective one can be easily made if one
does not wish to go to the expense of buying an instrument.
A strip of wood twelve or fourteen inches long and about two inches wide
has attached to its center a bridge-shaped piece of wood, a, Fig. 1. This
is covered with a brass plate, c, pierced with a hole one-half of an inch
in diameter. This hole extends through the wood, and is fitted with a
piston. Two long narrow inclined planes of nearly equal inclination, b,
b, grooved to slide on each other, are placed under the bridge; the lower
is to be fastened to the board; the end of the piston rests on the upper
one. The object from which we desire to cut a section is placed in the
hole, in the piston. If the upper plane be pushed in, the piston will be
forced upward, and with it the object. As the inclination of the plane is
very gradual, the vertical motion will be very slight as compared with
the horizontal.
When the object is raised a little above the brass plate, a keen edged
razor, thoroughly wet, is pushed over the hole, cutting the object. This
gives the section a smooth surface, and even with the plate; now push the
plane forward one-eighth to one-quarter of an inch, and cut again; this
will give a thin section of the object. The thickness of the section
depends, of course, on the distance the wedge is pushed.
With a little practice, much better sections can be cut by the hand than
by any machine; this does not apply of course to large sections. A razor
of good steel, with a blade thin and hard, are the most essential points
in an instrument for hand cutting. For ordinary purposes it is not
necessary to have the blade ground flat on one side, although many prefer
it. The knife should always be thoroughly wet, in order that the cut
tissue may float over its surface. Water, alcohol or salt and water may
be used for this purpose.
[Illustration: FIG. 1.]
_To out a section by hand_, hold the object between the thumb and first
two fingers of the left hand, supporting the back of the knife by the
forefinger. The knife is to be held firmly in the right hand, and in
cutting should never be pushed, but drawn from heel to point obliquely
through the tissue. The section should be removed from the knife by a
camel's hair brush.
When the object is too small to hold, it is usually _embedded_ in some
convenient substance. A carrot is sometimes very useful for this purpose.
A hole rather smaller than the object is cut out of the middle. Put
whatever is to be cut into this, and cut a thin section of the whole. The
carrot does not cling to either the knife or the section, and the knife
is wetted at every slice by it.
Paraffin is the agent usually employed for embedding purposes. Melt it,
and add a little lard to soften it; the addition of a little clove oil
renders it less adhesive.
Melt the paraffin at as low a temperature as possible, and pour it into a
paper cone. Dip the object into this and remove immediately; as soon as
the layer of paraffin surrounding it becomes hardened, replace it in the
paraffin; this prevents overheating the tissues.
Where the tissues are too soft to be cut, they may be soaked in a
solution of gum arabic and dried; in this condition they can be readily
cut, after which the gum can be dissolved off. This is an extremely
useful method for cutting the lung or other organs where an interstitial
support is needed. For a very thin object, a cork fitting any kind of a
tube is to be split, and the object placed between the two parts; the
cork is then thrust into the tube, and a sufficient degree of firmness
will be obtained to allow cutting. The sections should always be
manipulated with camel's hair brushes.
Much practice will be required before dexterity is attained.
_Methods of preserving the tissues_.--All water must be removed from the
tissue, either by drying or by immersing it in rectified spirits, and
then in absolute alcohol, and the alcohol driven off by floating it upon
oil of clove or turpentine. The substances used to preserve the tissues
are Canada balsam, Dammar balsam, glycerine, Farrant's solution,
potassium acetate, spirits, naphtha, and creosote.
The section is to be floated on to the slide or placed in position with a
camel's hair brush. It should be spread out, and then examined under the
microscope for the purpose of improving its position if necessary, or of
removing any foreign particles. A drop of the preserving medium is then
placed upon it, and another placed on the cover and allowed to spread
out. The cover is then taken by a pair of pincers and inverted over the
object, and one edge brought to touch the slide at one part of its
margin. The cover is then gently lowered, and the whole space beneath the
cover filled and the tissue completely saturated. If air bubbles show
themselves, raise the cover at one corner and deposit a further quantity
of the medium.
The slide should be set aside for a few days. First, the excess of the
medium must be removed; if it is glycerine, much of it can be removed by
a piece of blotting paper, but the cover must not be touched, for it is
easily displaced; that near the cover can be replaced by a camel's hair
brush. A narrow ring of glycerine jelly should be placed around the edge
of the cover, to fix it before the cement is applied. When this has set,
a narrow strip of cement is to be put on, just slightly overlapping the
edge of the cover and outside the margin of the jelly. Until it has been
perfectly secured, a slide carrying glycerine must never be placed in an
inclined position, as its cover will slide off.
_Preservative media_.--Canada balsam may be prepared as follows: Place
some pure Canada balsam in a saucer, and cover with paper to exclude
dust; dry it in an oven at a temperature of 150 deg.; when it cools, it will
become hard and crystalline. Dissolve this in benzole, and use in the
same way as glycerine.
Dammar is now used as a substitute for Canada balsam. By its use the
tissues are rendered more transparent. To prepare it, dissolve one-half
ounce of Dammar rosin and one-half ounce of gum mastic in three ounces of
benzole, and filter. This may be used to mount unsoftened bone and tooth,
hair, brain, and spinal column, and most tissues that have been hardened
in alcohol or chromic acid, which require to have their transparency
increased.
Glycerine is not adapted for white fibrous tissue or blood vessels,
unless they have been hardened in chromic acid, as it causes the white
fibers to swell up and lose their normal features. Sections of liver,
lung, skin, and alimentary canal show better in glycerine unless they
have been stained.
Farrant's solution may be substituted for glycerine in many instances,
because of its feebler tendency to render the tissues transparent. It
consists of equal parts of gum arabic, glycerine, and a saturated
solution of arsenious acid. In mounting preparations with this medium,
the covered object should be allowed to lie a day before the varnish is
applied, so that the cover may be fixed, and thereby prevented from being
displaced. Rectified spirits may be used for mounting softened bone and
tooth, and naphtha and creosote are useful for preserving urinary casts.
When the section is mounted in Canada or Dammar balsam, no cement is
required, but for all other preservative media the margin of the cover
must be covered with cement. To do this, dry the edges of the cover
thoroughly with bibulous paper, and paint a layer of gold size, allowing
it to overlap the cover an eighth or sixteenth of an inch, then cover
this with white zinc cement.
_Preparation for mounting the different tissues_.--To obtain a section of
bone or tooth requires a grinding down of the tissue until it is so thin
as to be transparent. A section should first be cut as thin as possible
by a fine saw. It should be attached by the flattest side to a piece of
glass, and then ground down by a grindstone or by very fine emery, on a
perfectly flat piece of lead. When sufficiently thin and transparent,
mount in rectified spirits or Dammar. Sections of the tongue may be made
by embedding in paraffin, and mounted in Farrant's solution or glycerine.
Sections of the stomach may also be made by embedding in paraffin, but
better ones can be made by freezing. Farrant's solution makes a good
mounting.
The intestines also give a better section from freezing than by
embedding, as the paraffin injures the villi; mount in the same medium as
the stomach.
The liver may be embedded in paraffin, and the section mounted in
Farrant's solution or glycerine. The kidney may be treated in the same
way. The cornea of the eye can be readily cut by embedding in paraffin,
and the section may be mounted in Farrant's solution. The crystalline
lens and retina may be treated similarly.
The brain and spinal cord should be embedded in paraffin or a carrot, and
the section mounted in Dammar. Sections of the uterus and ovaries are
best mounted in glycerine or Dammar. Sections of lung maybe made by
embedding in gum or by freezing, and mounted in Farrant's solution.
Every slide should be of uniform size, and labeled. The usual size is 3x1
inches, and should be of a good quality of glass, free from scratches or
air holes. They may be labeled either by writing with a diamond, or a
small piece of paper affixed to one end, on which is written what is
required.
* * * * *
LIFE HISTORY OF A NEW SEPTIC ORGANISM.
At a recent meeting in London, of the Royal Miscroscopical Society, Dr.
Dallinger gave his annual address to what was probably the largest
gathering of Fellows ever assembled on a similar occasion. After briefly
referring to the increased interest lately manifested in the study of
minute organisms, and recalling the characteristics of the doctrines of
abiogenesis and biogenesis, he passed rapidly in review the results of
the observations of Tyndall, Huxley, and Pasteur as bearing upon these
questions, and called attention to the observations of Buchner as to the
transformation of _Bacillus anthracis_ and _Bacillus subtilis_, and _vice
versa_, and referred with approval to Dr. Klein's criticisms thereon.
Having spoken of the desirability of careful and continuous study of this
class of organisms, and the importance of endeavoring to establish the
relation of the pathogenic form to the whole group, he said he should be
better able to deal with the subject by recording a few ascertained facts
rather than by making a more extended review, and he therefore devoted
the main part of his address to a description of "the life history of a
septic organism hitherto unknown to science." In his observations of this
form--extending over four years--he had the advantage of the highest
quality of homogeneous lenses obtainable, ranging from one-tenth to
one-fiftieth of an inch, his chief reliance being placed upon a very
perfect one thirty-fifth of an inch; and from the continuous nature of
the observations as well as the circumstances under which they were
carried on, dry lenses had for the most part to be employed. Having in
his possession a maceration of cod-fish in a fluid obtained from boiled
rabbits, he found at the bottom of it, when in an almost exhausted
condition, a precipitate forming a slightly viscid mass, to which his
attention was particularly directed. It was seen to contain a vast number
of _Bacterium termo_, but on examination with a one-tenth inch objective
showed that it also contained a comparatively small number of intensely
active organisms--one being discovered in about eight or ten drops of the
sediment. These measured 1-10,000 of an inch in length by 1-19,500 of an
inch in breadth. The fluid had originally been kept at a temperature of
90 deg. to 95 deg. F., and it was noticed that, when placed upon a cold stage
under the microscope, the movements of the organisms became, gradually
slower, until at last they entirely ceased; the necessity, therefore,
arose for the use of a warm stage, and the very ingenious contrivance by
which a continuous and even temperature was maintained within the
one-tenth of a degree was exhibited. The greatest difficulty in the
matter was, however, experienced in obtaining specimens for observation,
in order to be able to trace them from their earliest to their latest
stage. The President then explained, by means of an admirable series of
illustrations projected upon a screen by the oxyhydrogen lantern, the
life history of the organism to which he had referred, exhibiting it
first as a translucent, elliptic, spindle-shaped body, with six long and
delicate flagella, the various positions in which the five specimens were
drawn giving a very good idea of its peculiar porpoiselike movements.
The various positions which it assumed in making an attack upon a portion
of decomposed matter were also shown, the movements quite fascinating the
observer by their rhythmical character. The supposed action of the
flagella in the production of the movements observed was explained,
distinct evidence being afforded of a remarkable spiral motion, at least
of those behind. The process of fission was illustrated in all its
observed stages from the first appearance of a construction to that of
final and complete separation, the whole being performed within the space
of eight or nine minutes. A description of the process of fusion from the
simple contact of two organisms to their entire absorption into each
other followed, as well as their transformation into a granular mass,
which gradually decreased in size in consequence of the dropping of a
train of granules in it wake as it moved across the field. The
development of these granules was traced from their minute semi-opaque
and spherical form to that of the perfect flagellate organism first
shown, the entire process being completed in about an hour. Experiments
as to their thermal death-point showed that, while the adults could not
be killed by a temperature less than 146 deg. F., the highest point endured
by the germs was 190 deg. F. Illustrations of a variety of other modes of
fission discovered in previous researches on similar forms were given,
showing the mode of multiple division and a similar process in the case
of an organism contained in an investing envelope. The President
concluded his address, which was listened to throughout with the greatest
attention, by remarking that, though the processes could be seen and
their progress traced, the _modus operandi_ was not traceable. Yet the
observer could not fail to be impressed with the perfect concurrent
adaptation of these organisms to the circumstances of their being; they
were subject to no caprices, their life-cycles were as perfect as those
of a crustacean or a bird, and while the action of the various processes
was certain, their rapidity of increase and the shortness of their life
history were such that they afforded a splendid opportunity of testing
the correctness of the Darwinian law.
* * * * *
WINTER AND THE INSECTS.
For a number of years previous to 1878 we had in Pembroke but little or
no severe cold, owing to the prevalence of southeast, south, west, and
especially southwest winds. In many places, fuchsias that were left in
the ground for the entire year had not been frozen to the root within the
memory of man. Some of these plants had grown to be trees five or six
yards in height, and with a trunk the size of one's leg. Now, during the
same series of years, many insects that are common throughout the rest of
Great Britain did not cease to be rare with us, or rather were confined
to certain circumscribed limits. Thus, the Noctuellae, with the exception
of a few species abundant everywhere, were almost wanting, and I know of
no other country where the dearth of common species of nocturnal
butterflies was so great. But during the winter of 1878 there supervened
a radical change. Persistent winds from the northwest, driving back the
currents of warm air from the south, brought on an intense cold that
froze everything; or, when some variation occurred in them, clouds formed
and dissolved into a rain that immediately froze, so that the large roads
remained for weeks covered with a layer of rime from two to four inches
thick.
[Illustration: GREEN WOODPECKER SEARCHING FOR INSECTS.]
The winters of 1879 and 1880 were equally cold; we may even say that the
latter was the severest that had been experienced in fifty years. This
year the sea-sand, along with the ice and snow, formed a thick crust all
along the tide-line--this being something rarely seen along our coast.
The first of these three winters (1878-1879) killed all the arborescent
veronicas and a few sumacs. As for the fuchsias and myrtles, they were
frozen down to the level of the soil.
I now come to the effects of this severe cold upon the insects.
The Lepidoptera, which before were rare, became more and more common in
1879, 1880, and 1881, and so much so that during the last named year they
abounded; and species that had formerly been detected only at certain
favored points spread over the entire coast and into the interior of the
country. The geometers appeared in numbers that were unheard of. But this
change was especially striking as regards the Noctuellae, in view of the
previous rarity of the individuals belonging to this family.
We have here an example of the direct relation of cause to effect,
although I am not in a position to assert that the effect is always
produced in the same way. To me there is no question as to the fact that
the constitution of those insects which nature has accorded the faculty
of liberating is strengthened, and that their chances of life are
increased, if the cold of winter is intense enough to plunge them into an
absolute rest, and is not unseasonably affected by warm, spring-like
days. It is certain that such cold is capable of contributing largely to
the multiplication of the individuals of such species as hibernate in the
egg state, and it also has a beneficent influence upon those species
which, like the small social larvae, pass this season upon the earth
enveloped in a silken envelope, or, like the larvae of the Noctuellae,
between dead leaves or upon the ground itself.
On another hand, it cannot be doubted that mild winters greatly
contribute to the bringing about of a destruction of larvae and chrysalids
in two ways: First, they favor the development of mould, which, as well
known, attacks the larvae of insects when these have been enfeebled by an
excess of rain or dampness; and second, they permit beasts of prey to
continue to exercise their activity. Now, these latter are numerous.
Moles, instead of burying themselves deeply, then continue to excavate
near the surface, and shrew mice are constantly in search of food. These
small mammals, which abound in this district, destroy a large number of
chrysalids of Lepidoptera.
It is the same with birds. As soon as severe cold begins to prevail in
the north and east, they come in troops to the open fields and the
sheltered slope of the hills of our district. But it is scarcely worth
while to stop to tell of the skill and perseverance of these destroyer of
larvae. We may mention, the woodpecker, however, as a skillful searcher
for insects that lie hidden in places where the sun has melted the snow.
The carnivorous Coleoptera and the Forficulae are likewise generally in
motion during mild winters. Doubtless these last-named do not make very
large inroads in the ranks of larvae and chrysalids every day; yet, having
no other food, they destroy a goodly number of them. But I believe that
the devastations made in the army of insects by all these enemies united
do not equal those made by certain crustaceans--the wood lice.
During mild winters these pests multiply, eat, and prosper out of bounds,
and to such a point that, in a climate like ours, they become a true
scourge that prevails everywhere, out of doors and within. Once in a
place, they begin to look for larvae and chrysalids, which they devour.
The severe cold seems to have destroyed a certain number of them, since
they are now not so numerous by far; and it has at least certainly put a
stop to their devastations at an epoch when the larvae are more
particularly exposed to the attacks of their enemies. It is to this
cause, as well as to the preceding, that I am led to attribute the
extraordinary multiplication of so many species during the three last
summers, which were separated by severe winters. Last winter was mild,
and there is therefore no reason to expect that there will be another
multiplication; but I hope that the harm done by such a season will be
slight. It is the progressive multiplication of the destroyers, joined to
the correlative disappearance of the victims caused by a series of
temperate seasons, that is to be feared.
In support of the proposition that I maintain, I may mention still
another fact. While this district (Pembroke, Wales) is relatively poor in
species whose larvae feed and hibernate in the open air a few species of
Noctuellae, whose larvae live buried in the earth, are always abundant. The
country is relatively rich in spices of _Tortrix_, which develop and
hibernate in the stalks or roots of plants. It is also worthy of remark
that very few of our species seem to be incapable of enduring a severe
winter.--_C.G. Barret, in Science et Nature_.
* * * * *
SILK WORM EGGS.
Prof. C.V. Riley, entomologist, announces that the Department of
Agriculture, Washington, will purchase during the coming summer such
quantities of silk worm eggs as may be deemed necessary for the
distribution that it is proposed to make for the season of 1886. So far
as found practicable, the eggs will be purchased of American producers.
There are certain precautions, however, that must be taken to insure
purchase. Eggs of improved races only (preferably of the French or
Italian Yellow Races) will be bought, and the producer should send one or
two samples of pierced cocoons with the eggs. In addition to this the
producer must conform to certain rules to be hereafter explained, so that
an examination may be made that will serve to show the degree of purity
of the eggs. No silk culturist should use his crop for the production of
eggs unless the worms have shown, until they began the spinning of their
cocoons, every sign of perfect, robust health. Any indication of the
disease called _flacherie_, from which the worms so often die after the
fourth moult and turn black from putrefaction, or of any other disease
from which silk worms suffer, should be considered as ample reason for
not using the cocoons for the purpose in question. They should, on the
other hand, be sold for the filature. If the worms have all the
indications of health until the spinning period, then the cocoons may be
used for the production of eggs. The following brief instructions will
prove of service to those who which to secure sound eggs:
[Illustration]
For each ounce of eggs to be produced, about three-quarters of a pound of
fresh cocoons from the finest and firmest in the lot should be chosen.
These should be strung in sets upon a thread, care being taken not to
pierce the chrysalis, and the strings hung in a cool, darkened room. The
moths generally emerge from the cocoons early in the morning, and will be
seen crawling about over these, the males being noticeable by their
smaller abdomens, more robust antennae, and by their greater activity. The
moths should be placed, regardless of sex, on a table, where they will
soon find their mates and couple. As soon as formed, the couples should
be removed to another table, that they may not be disturbed by the
flutterings of the single moths.
There should be prepared for each ounce of eggs to be produced, about
one hundred small bags of fine muslin, made in the following manner: Cut
the cloth in pieces 3x6 inches. Then fold one end over so as to leave a
single edge of about three-quarters of an inch, as shown in the
accompanying cut. This should be sewn up into a bag with the upper end
open, and then turned inside out, so that the seams will cause the sides
to bulge. Thus completed they are called "cells." The cells should be
strung on a cord stretched across the room.
The moths couple as a rule about eight o'clock in the morning. About four
in the afternoon they should be separated by taking them by the wings and
drawing them gently apart. Each female should now be placed by herself in
a cell, which is then closed by a pin as shown in the figure. Here she
will lay her eggs and in due time die. The males may as a rule be thrown
away, but it is wise to keep a few of the more active ones, in case there
should be a superabundance of females the following day.
When the females have finished laying their eggs, which operation
occupies about thirty-six hours, they are ready to be shipped to this
office. The cells, with their inclosed moths and eggs, should be placed
in a strong box of wood or tin, being packed in such a manner that they
will not be crushed, and mailed to the entomologist at the department. By
using the inclosed return penalty slip, payment of postage may be
avoided. The name of the sender should be placed in each box. The moths,
as soon as received, will be examined microscopically, and the eggs of
those which are found to be free from disease will be weighed and paid
for at the rate of $2.50 per ounce of 25 grammes (about 6-7 of an ounce
avoirdupois). Silk culturists are advised not to attempt the production
of eggs unless they are adepts at the industry, and have had at least one
season's experience. We would advise each person desiring to sell, to
send a sample first, with a statement of the quantity offered.
* * * * *
Dr. Zintgraff of Bonn has taken a phonograph with him to Africa. He
intends to bring home phonograms of the savage dialects which he will
hire the natives to speak into the machine.
* * * * *
[NATURE.]
DETERMINING THE MEAN DENSITY OF THE EARTH.
In _Nature_ for March 5 (p. 408) Prof. Mayer suggests an improvement in
our method of determining the mean density of the earth, from which it
appears that our plan has not been properly understood. This
misunderstanding, no doubt, has arisen from the incomplete description of
our method given in the _Nature_ (Jan. 15. p. 260) report of the
_Proceedings_ of the Berlin Physical Society, which report was probably
the only source of information accessible to Prof. Mayer. We are led
therefore to give a short description of our method.
Let H I K L represent a section of a cubical block of lead, about two
meters in the edge, and weighing 100,000 kilos. The balance, A B C, is
placed in the middle of the upper horizontal surface. It bears the
scale-pans, D and E. Under these scale-pans the block is bored vertically
through, and two other scale-pans, F and G, are suspended below the
block, attached to the balance by means of rods passing through these
openings.
A weight D is brought into equilibrium by weights in G. The weight in D
is acted upon by the earth's attraction + that of the block, and that in
G by the earth's attraction - that of the block. The weights in G are then
greater than that in D by twice the attraction of the block. The weight
in D in now removed to F, and counterbalanced by weights in E. The weight
in E will be less than that in F by twice the attraction of the block.
The difference of the two weighings gives therefore four times the
attraction of the block. A correction must be introduced for the
variation in the earth's attraction due to the different heights of D, E
and F, G.
[Illustration]
In order to obtain as great a deflection of the balance by the method
suggested by Prof. Mayer, each of the mercury spheres must exert the same
attraction as our lead block. This would require spheres having radii of
about one meter. The length of the beam of the balance would be
necessarily at least two meters. Besides, each mass of mercury, would
exert some attraction on the weight on the other side, and thus lessen
the deviation of the balance.
The method given by Prof. Mayer, except for the suggested employment of
mercury, is then no improvement on ours. If we should use mercury, we
would construct a cubical vessel to contain it, and use it as we propose
to use the lead block. The advantage of using mercury is, however,
counterbalanced by the difficulty of obtaining it in such large
quantities as would be necessary.
ARTHUR KONIG.
FRANZ RICHARZ.
Berlin, Physical Institute of the University, March 15.
* * * * *
PHYSICS WITHOUT APPARATUS.
_The Porosity and Permeability of Bodies._--Take two tumblers of the same
size, place one of them upon a table, and pour into it a small quantity
of nearly boiling water. Cover this glass with a sheet of cardboard, and
invert the other one upon it. This second tumbler must be previously
wiped so as to have it perfectly dry and transparent. In a few seconds
the steam from the lower tumbler will traverse the cardboard (which will
thus exhibit its permeability), and will gradually fill the upper
tumbler, and condense and run down its sides. Wood and cloth may be
experimented with in succession, and will give the same results; but
there are other substances that are _impermeable_, and will not allow
themselves to be traversed. Such, for example, is the vulcanized rubber
of which waterproofs are made. This experiment explains to us why fog
is, as has been well said, so _penetrating_. It traverses the tissue of
our overcoat and of our flannel, and comes into contact with our body. On
the contrary, a rubber coat preserves us against its action.
[Illustration: Fig. 1.--EXPERIMENT UPON THE PERMEABILITY OF BODIES.]
_A Hot Air Balloon_.--Make a hollow cylinder of small diameter out of a
sheet of paper such as is used for cigarette packages, and turn in the
ends slightly so that it shall preserve its form. If the cylinder seems
too difficult to make, a cone may be substituted. Now set fire to the
cylinder or cone at its upper part. The paper will burn and become
converted into a thin sheet of ashes, which will contract and curl
inward. This light residuum of ashes, being filled with air rarefied by
combustion, will suddenly rise to a distance of two or three yards. Here
we have a Montgolfier balloon.--_La Nature_.
[Illustration: Fig. 2.--PRINCIPLE OF THE HOT AIR BALLOON.]
* * * * *
THE CASINO AT MONTE CARLO.
The little city is situated about half way between Nizza and Mentone, and
it formerly was the chief city of a principality that belonged to the
family Grimaldi. Prince Florestan sold in 1860 his royal prerogatives to
the Emperor Napoleon, for three million francs, consequently the land
came under the jurisdiction of the French republic, but the city remained
in the Prince's possession, who, however, gave to the gambler Blanc the
privilege of erecting a gambling house upon the rocky shore of the sea.
[Illustration: THE CASINO AT MONTE CARLO.]
Enormous sums of money were spent to give this isolated cliff its present
appearance, covered as it is with beautiful buildings, hotels, and
villas, besides the magnificent Casino building, which was erected in
1862. Directly facing the sea, there is a succession of most beautiful
gardens and terraces.
But this establishment, which seems like paradise, has had a most
disastrous effect upon thousands of persons, and for a long time the
subject of influencing the French government to put a stop to this
gambling house has been agitated. It can scarcely be imagined how much
misery it has already caused. It is evident to every one that the keeper
of the bank makes considerable profit, as the chances are 63 times
greater in his favor than those of the player.
It is admitted that the profits amount every year to 17 million francs.
One can well imagine how many fortunes have been consumed every year to
make this profit; but the number cannot be determined.
* * * * *
ON AN EXPRESS ENGINE.
It is a somewhat unpromising morning--the river is dark with fog and the
huge arch of the station nearly hidden by mist and steam. A cold, damp
wind makes the passengers hurry into the carriages, and strikes us
sharply as we step on to the foot-plate of the engine, which has just
joined the train. But as we get behind the shelter of the screen, we feel
a generous and slightly unctuous sensation of warmth very comforting to a
chilly man. The brasswork of the engine shines brilliantly, the footboard
has been newly scrubbed, and the driver and stoker stand waiting for the
signal. The needle shows that the steam is just below the pressure at
which it would begin to blow off; the water in the gauge glass is just
where it ought to be; in fact, the engine is in perfect condition and
ready for a start. The line is clear, the guard's whistle is answered by
our own, and we glide almost imperceptibly past the last few yards of the
platform. The driver opens the regulator till he is answered by a few
sounding puffs from the funnel, and then stands on the lookout for
signals so numerous that one wonders how he can tell which of the many
waving arms is raised or lowered for his guidance.
So he goes on, with hand on regulator and lever, gradually admitting more
steam as signal after signal comes nearer and then flies past us, till at
last we are clear of the suburbs and find ourselves on a gentle incline
and a straight road, with the open fields on either side. It is now that
the real business of the journey begins. Locomotives are as sensitive and
have as many peculiarities as horses, and have to be as carefully studied
if you would ride them fast and far. The lever is put into the most
suitable notch for working the steam expansively; the driver's hand is on
the regulator, not to be removed for the rest of the trip; the furnace
door is thrown wide open, and firing begins in earnest. Here it may not
be amiss to state, for the benefit of the uninitiated, that the regulator
controls the supply of steam from the boiler, while the lever enables the
driver to reverse the engine, or, as we have already stated, to expand
the steam by cutting it off before the end of the stroke. The engine
answers to the appeal like a living thing, and seems, with its steady
beat and sonorous blast, to settle down to its work. It is pleasant from
our seat in the corner of the screen to see this preparation for the work
ahead--the absolute calm of driver and stoker, who exchange no word, but
go steadfastly and quietly about their business; to feel the vibrations
from the rails beneath throb through one with slowly increasing rapidity,
or watch the trees and houses go past as gulls flap past a boat. For
there is a certain apparent swagging movement of the objects past which
one travels which can only be likened to the peculiar flight of a large
sea-bird. But now there are signs of increased activity on the
foot-plate; the stoker is busy controlling the feed of water to the
boiler, and fires at more frequent intervals; the driver's hand moves
oftener as he coaxes and encourages the engine along the road, his
slightest gesture betraying the utmost tension of eye and ear; the
stations, instead of echoing a long sullen roar as we go through them,
flash past us with a sudden rattle, and the engine surges down the line,
the train following with hot haste in its wake. We are in a cutting, and
the noise is deafening. Looking ahead, we see an apparently impenetrable
wall before us. Suddenly the whistle is opened, and we are in one of the
longest tunnels in England. The effect produced is the opposite of that
with which we are familiar in a railway carriage, for the change is one
from darkness to light rather than from light to darkness. The front of
the fire-box, foot-plate, and the tender, which had been rather hazily
perceived in the whirl of surrounding objects, now strike sharply on the
eye, lit up by the blaze from the fire, while overhead we see a glorious
canopy of ruddy-glowing steam. The speed is great, and the flames in the
fire-box boil up and form eddies like water at the doors of an opening
lock. Far ahead we see a white speck, which increases in size till the
fierce light from the fire pales, and we are once more in open day. The
weather has lifted, the sky is gray, but there is no longer any
appearance of mist. The hills on the horizon stand out sharply, and seem
to keep pace with us as the miles slip past. The line is clear; but there
is an important junction not far distant, and we slacken speed, to insure
a prompt pull-up should we find an adverse signal. The junction signals
are soon sighted; neither caution nor danger is indicated, and, once
clear of the station, we steam ahead as fast as ever. One peculiarity of
the view of the line ahead strikes us. Looking at a railroad line from a
field or neighboring highway, even where the rails are laid on a steep
incline, the rise and fall of the road is not very strikingly apparent.
Seen through the weather-glass, the track appears to be laid up hill and
down dale, like a path on the downs above high cliffs. Over it all we
advance, the engine laboring and puffing on one or two heavy gradients,
in spite of a full supply of steam, or tearing down the inclines with
hardly any, or none at all and the brake on. And here it may be noted
that, like modern men, modern engines have been put upon diet, and are
not allowed to indulge in so much victual as their forefathers. The
engine-driver, like the doctor of the new school, is determined not to
ruin his patient by over-indulgence, and will tell you severely enough
that "he will never be guilty of choking his engine with an over-supply
of steam." In the mean time, the character of the country we travel
through has changed. It has become more open, and there is a stiff
sea-breeze, which makes itself distinctly felt through the rush of air
produced by the speed at which we are going. We fly past idle streams and
ponds, and as the steam swirls over them are disappointed at producing
so little effect; but the ducks, their inhabitants, are well used to such
visitations, and hardly deign to move a feather. Suddenly we plunge into
a series of small chalk cuttings, and on emerging from them find
ourselves parallel with a grand line of downs. We speed by a curve or
two, and find ourselves on the sea-shore; one more tunnel, and with steam
off we go soberly into the last station. But there is one step more. The
breeze blows about our ears. Before us the rails are wet, for the sea
swept over them not many hours since, and to accomplish the last few
yards of our journey the lever controlling the sand-box must be used
liberally, to prevent slipping; the signal is given, and at a walking
pace we make our way to where the steamer is awaiting us. A gentle
application of the brake pulls us up, and the journey is over. It is
difficult to realize, as the engine stands quietly under the lee of the
pier while the driver examines the machinery, and the fire, burned low,
throws out a gentle warmth as we stand before it, that half an hour ago
we were tearing along the line at full speed, while the foot-plate that
is now so pleasant to lounge on throbbed beneath us. Nothing now remains
but to kill time as best we may till the return trip many hours hence. It
scarcely promises to be as comfortable as our morning ride, for the
weather has changed--it is blowing half a gale, and the rain comes down
in sheets. Our train is timed to start in the small hours, and the night
seems dirty and depressing enough as we make our way for a cup of coffee
to the refreshment room, where a melancholy Italian sits in sad state
eating Bath buns and drinking brandy. We walk past the train, laden with
miserable sea-sick humanity, and step on the engine, which stands in the
dark at the end of the platform. Time is up, and we pass from the dim
half-light of the station into outer darkness. A blacker night there
could hardly be; looking ahead there is nothing to be seen but one's own
reflection in the weather-glass. We are in the midst of obscurity, which
suddenly changes to a rich light as the whistle is opened and we enter a
tunnel. The effect is far more striking than in the daytime. The light is
more concentrated, and the mouth of the tunnel we have just entered might
be the entrance to Hades--for there is no telltale spot of light to prove
to our senses the existence of any opening at the other end. The sound
echoed from the walls and roof has a tremendous quality, and resolves
itself into a grand sort of Wagnerian rhythm, making a vast crescendo,
till with a rush we clear the tunnel, and are once more under the open
sky. The pace is increasing, the steady beat of the engine tells more
distinctly on the ear than in the daytime; the foot-plate is lit up by
the glare from the fire-door; but still there is nothing to be seen ahead
but the impenetrable night. Looking back, however, the scene is very
different. The tender and guard's van glow in the light thrown by the
fire, trees and houses by the side of the track stand out sharply for a
moment and are then lost to sight, the light from the carriage windows
produces the effect of the wake of a ship seen from the stern. Gradually
the clouds have rolled away, leaving the sky clear. The moon is seen
fitfully through the whirling steam; the surrounding country is visible
for miles round. The effect produced is unspeakably beautiful. In the
mean time let us turn our attention to the working of the engine. In the
first place, let us take note that, although the engine we are now on,
and that which took us from London, belong to the same type, their
performances are somewhat different. No two engines ever resemble each
other, no matter how carefully they may have been built from the same
plan, neither do any two drivers manage their engines precisely in the
same way. We have in this instance an excellent opportunity of comparing
two different methods of driving. It is the driver's principal object to
get the required amount of work out of his engine with the smallest
possible expenditure of coal and water. To obtain this result the steam
must be worked expansively, which is done by placing the valve gear in
such a position by means of the lever that the supply of steam to the
cylinders is cut off, as we have stated at the beginning of this article,
before the piston has accomplished its full stroke. There are two ways of
controlling the speed of an engine worked, as all locomotives are worked
now, expansively. You may keep the regulator wide open, so that there is
always a full supply of steam on its way to the cylinders, in which case
you increase or diminish the speed by using the steam more or less
expansively through the agency of the lever. Or you may work with the
same amount of expansion throughout the journey, and have command of the
engine by constantly changing the position of the regulator. There is no
doubt that the men who employ the latter method save something by it,
although this would hardly seem to be the opinion of the driver who is
bringing us rapidly nearer to London, for unlike the driver whom we
accompanied on the daylight journey, his hand is not often on the
regulator. As we rush on past countless signals, punctual to the minute,
yet always having ample time to slacken speed before we come to the
places where the different colored lights cluster thickest, we are
reminded once more how much is required of an express engine-man besides
a thorough acquaintance with the machinery he has to control. Traveling
at night at a great speed, he must know every inch of the road by
heart--where an incline begins and where it ends, and the exact spot at
which every signal along the line may be first sighted. He must have
completely mastered the working of the traffic on both the up and down
lines, and, above all, must be ready to act with the utmost promptitude
should anything go wrong. Mr. Michael Reynolds' publications have done
much toward enlightening the public on these points, but we doubt if
there are many who really know the amount of toil and danger cheerfully
faced by the men on the engine, who hold their lives in their hands day
after day for many years. These thoughts occur to us as we recross the
Thames and pull up at the platform after a thoroughly enjoyable
run.--_Saturday Review_.
* * * * *
The mucilage on postage stamps may not be unhealthy, but persons having a
good many to affix to letter envelopes, circulars, newspapers, or other
wrappers every day, will consume considerable gum during a year. A less
objectionable mode of affixing stamps than the one usually employed is to
wet the upper right hand corner of the envelope, and press the stamp upon
it. It will be found to adhere quite as well as if the stamp went through
the moistening process.
* * * * *
ERYTHROXYLON.
[Footnote: From an "Ephemeris of Materia Medica, Pharmacy, Therapeutics,
and Collateral Information." By Edward E. Squibb, M.D., Edward H. Squibb,
S.B., M.D., and Charles F. Squibb, A.B.]
COCA.
The condition of the principal markets of the world for this drug has
recently been exceptionally bad. That is, whether good coca was sought
for in the ports of Central and South America, or in London, Hamburg, or
New York, the search, even without limitation in price, was almost
invariably unsuccessful. Not that the drug, independent of quality, was
scarce, for hundreds of bales were accessible at all times; but the
quality was so poor as to be quite unfit for use. The samples, instead of
being green and fragrant, were brown and odorless, or musty and
disagreeable, at once condemning the lots they represented, to the most
casual observation, and yet the price was high enough to have represented
a good article. The best that could be done by the most careful buyers
was to accept occasional parcels, the best of which were of very inferior
quality, and therefore unfit for medicinal uses, and these at very high
prices. Coca is well known to be a very sensitive and perishable drug,
only fit for its somewhat equivocal uses when fresh and green, and well
cared for in packing and transportation. Very much like tea in this and
other respects, it should be packed and transported with the same care
and pains, in leaded chests, or in some equivalent package. It is very
well known that tea, if managed, transported, handled, and sold as coca
is, would be nearly or quite worthless, and therefore coca managed as the
great mass of it is must be nearly all of it comparatively worthless. If
used as tea is, this would probably soon appear; but when used as a
medicine which has been highly extolled and well advertised, it seems to
go on equally well whether of good or bad quality. It is pretty safe to
say that nineteen-twentieths of the coca seen in this market within the
past two years must be almost inert and valueless, yet all is sold and
used, and its reputation as a therapeutic agent is pretty well kept up.
At least many thousands of pounds of the brown ill-smelling leaf, and of
preparations made from it, are annually sold. And worse than this,
considerable quantities of a handsome looking green leaf, well put up and
well taken care of, have been sold and used as coca, when wanting in
nearly all its characteristics.
The writer for more than a year past has seen but one or two small lots
of moderately good coca, and in common with other buyers has been obliged
to buy the best that could be found to keep up his supply of the fluid
extract. Almost every purchase has been made on mental protest, and he
has been ashamed of every pound of fluid extract sent out, from the
knowledge that it was of poor quality; and there seems to be no more
prospect of a supply of better quality than there was this time last
year, because so long as an inferior quality sells in such enormous
quantities at good prices the demands of trade are satisfied.
Under this condition of the markets, the writer has finally decided to
give up making a fluid extract of coca, and has left it off his list,
adopting a fluid extract of tea instead, as a superior substitute, for
those who may choose to use it, and regrets that this course was not
taken a year ago.
The character of coca as a therapeutic agent is not very good. The florid
stories of a multitude of travelers and writers, up to and including the
testimony of Dr. Mantegazza, received a considerable support from so good
an authority as Sir Robert Christison, who reported very definite results
from trials made upon himself, and upon several students under his
immediate control and observation; and his results seem to have led to a
very careful and exhaustive series of observations at University College,
London, by Mr. Dowdeswell. This paper, published in _The Lancet_ of April
29 and May 6, 1876, pp. 631 and 664, is entitled "The Coca Leaf:
Observations on the Properties and Action of the Leaf of the Coca Plant
(Erythroxylon coca), made in the Physiological Laboratory of University
College, by G.F. Dowdeswell, B.A." The results of these investigations
were absolutely negative, and at the close of the work the investigator
says: "Without asserting that it is positively inert, it is concluded
from these experiments that its action is so slight as to preclude the
idea of its having any value either therapeutically or popularly; and it
is the belief of the writer, from observation upon the effect on the
pulse, etc., of tea, milk and water, and even plain water, hot, tepid,
and cold, that such things may, at slightly different temperatures,
produce a more decided effect than even large doses of coca, if taken at
about the temperature of the body."
Conflicting and contradictory testimony from competent authority is not
uncommon in therapeutics, and the reasons for it are well recognized in
the impossibility of an equality in the conditions and circumstances of
the investigations, and hence the general decision commonly reached is
upon the principle of averages.
There can hardly be a reasonable doubt that coca, in common with tea and
coffee and other similar articles, has a refreshing, recuperative, and
sustaining effect upon human beings, and when well cultivated, well
cured, and well preserved, so as to reach its uses of good quality and in
good condition, it is at least equal to good tea, and available for
important therapeutic uses. Mr. Dowdeswell supposed that he used good
coca, but it is very easy to see that with any amount of care and pains
he may have been mistaken in this. Had he but used the same parcel of
coca that Sir Robert Christison did, the results of the two observers
would be absolutely incomprehensible; and the results, in the absence of
any testimony on that point, simply prove that the two observers were
using a different article, though under the same name, and possibly with
the same care in selection. On Sir Robert Christison's side of the
question there are many competent observers whose testimony is spread
over many years; while on Mr. Dowdeswell's side there are fewer
observers. But there has been no observer on either side whose researches
have been anything like so thorough, so extended, or so accurate as those
of Mr. Dowdeswell. Indeed, no other account has been met with wherein the
modern methods of precision have been applied to the question at all; the
other testimony being all rather loose and indefinite, often at second or
third hands, or from the narratives of more or less enthusiastic
travelers. But if Mr. Dowdeswell's results be accepted as being
conclusive, the annual consumption of 40,000,000 pounds of coca at a cost
of 10,000,000 dollars promotes this substance to take rank among the
large economic blunders of the age.[9]
[Footnote 9: An excellent summing up of the character and history of
coca, from which some of the writer's information has been obtained, will
be found in "Medicinal Plants," by Bentley and Trimen, vol. i., article
40.]
The testimony in regard to the effects of tea, coffee, Paraguay tea,
Guarana and Kola nuts, is all of a similar character to that upon coca.
Each of these substances seems to have come into use independently, in
widely separated countries, to produce the same effects, namely, to
refresh, renew, or sustain the physical and mental organism, and it was a
curious surprise to find, after they had all been thus long used, that
although each came from a different natural order of plants, the same
active principle--namely, caffeine--could be extracted in different
proportions from all. It is now still more curious, however, to find that
for centuries another plant, namely coca, yielding a different principle,
has been in use for similar purposes, the effects of which differ as
little from those of tea, coffee, etc., as these do among themselves. Yet
cocaine is chemically very different from caffeine, simply producing a
similar physiological effect in much smaller doses. All these substances
in their natural condition seem to be identical in their general
physiological effect, but idiosyncrasy, or different individual
impressibility or sensitiveness, causes a different action, as well in
quality as in degree from the different substances, upon some persons.
In order to throw a little additional light on the comparative activity
of the principal individuals of this group of substances, the following
trials were made. It is generally admitted, and is probably true, that
the same power in these agents which refreshes, recuperates, and sustains
in the condition which needs or requires such effects also counteracts
the tendency to sleep, or produces wakefulness when a tendency to sleep
exists; and, therefore, if a tendency or disposition to sleep could be
prevented by these agents, this tendency might be used as a measure of
their effects when used in varying quantities, and thus measure the
agents against each other for dose or quantitative effect. In this way
the proposition is to first measure coca against tea, then coffee against
guarana, and finally to compare the four agents, using pure caffeine as a
kind of standard to measure by.
An opportunity for such trials occurred in a healthy individual
sixty-five years old, not habituated to the use of either tea, coffee,
tobacco, or any other narcotic substances, of good physical condition and
regular habits, and not very susceptible or sensitive to the action of
nervines or so-called anti-spasmodics. Quantities of preparations of
valerian, asafoetida, compound spirit of ether, etc., which would yield a
prompt effect upon many individuals seem to have little or no effect upon
him, nor do moderate quantities of wines or spirits stimulate him. That
is to say, he has not a very impressible nervous organization, is not
imaginative, nor very liable to accept results on insufficient or partial
evidence.
Fully occupied with work, both physical and mental in due proportion, for
more than ten hours every secular day, when evening comes he finds
himself unable to read long on account of a drowsiness supposed to be of
a purely physiological character. With a full breakfast at about 7:30, a
full dinner at about 2:30, and a light evening meal about 7, and no
stimulants, or tea, or coffee at any time, he finds, as a matter of not
invariable but general habit, that by half past 8 drowsiness becomes so
dominant that it becomes almost impossible, and generally impracticable,
to avoid falling asleep in his chair while attempting to read, even
though ordinary conversation be carried on around him.
The first trial to combat or prevent this drowsiness was made with
caffeine. The first specimen used was a very beautiful article made by
Merck of Darmstadt, and after that by pure specimens made for the
purpose, the two kinds being found identical in effect.
Commencing with a one grain dose at about 6:30 P.M., on alternate
evenings, leaving the intermediate evenings in order to be sure that the
nightly tendency still persisted, and increasing by half a grain each
alternate evening, no very definite effect was perceived, until the dose
reached 21/2 grains, and this dose simply rendered the tendency to sleep
resistible by effort. After an interval of three evenings, with the
tendency to sleep recurring with somewhat varying force each evening, a
dose of 3 grains was taken, the maximum single dose of the German
Pharmacopoeia. This gave a comfortable evening of restedness, without
sleep or any very strong tendency to it until ten o'clock. Without
anything to counteract sleep, the rule was to read with difficulty by
nine, without much comprehension by quarter past nine, and either be
asleep or go to bed by half past nine. The 3 grain dose of caffeine
repeatedly obviated all this discomfort up to ten o'clock, but did not
prevent the habitual, prompt, and sound sleep, from the time of going to
bed till morning.
This was the model established, upon and by which to measure all the
other agents, and they were never taken nearer than on alternate
evenings, with occasional longer intervals, especially when the final
doses of record were to be taken.
The next agent tried in precisely this same way was coca; and knowing
that the quality of that which was attainable was very low, the
commencing dose of the leaf in substance was 2 drachms, or about 8
grammes. This gave no very definite effect, but 21/2 drachms did give a
definite effect, and a subsequent dose of 21/2 fluid drachms of a well made
fluid extract of coca gave about the same effect as 21/2 grains of
caffeine. Three fluid drachms of the fluid extract were about equivalent
to 3 grains of caffeine.
Both the coca used and the fluid extract were then assayed by the modern
methods, for the proportion of the alkaloid they contained.
The only assays of coca that could be found conveniently were those of
Dr. Albert Niemann, of Goslar, given in the _American Journal of
Pharmacy_, vol. xxxiii., p. 222, who obtained 0.25 per cent.; and of
Prof. Jno. M. Maisch, in the same volume of the same journal, p. 496, who
obtained 4 grains of alkaloid from 1,500 grains of coca, which is also
about a quarter of one per cent. These assays were, however, very old,
and made by the old process. The process used by the writer was the more
modern one of Dragendorff slightly modified. It was as follows:
Thirty grammes of powdered coca, thoroughly mixed in a mortar with 8
grammes of caustic magnesia, were stirred into 200 c.c. of boiling water,
and the mixture boiled for ten minutes. The liquid was filtered off, and
the residue percolated with about 60 c.c. of water. It was then again
stirred into 150 c.c. of boiling water, and was again boiled and
percolated until apparently thoroughly exhausted. The total liquid,
amounting to more than 600 c.c., was evaporated on a water-bath,
commencing with the weaker portions, so that the stronger ones might be
exposed to the heat for the shortest time, until reduced to about 20 c.c.
This liquid extract was transferred to a flask, and vigorously shaken
with 50 c.c. of strong ether. The ether was poured off, as closely as
practicable, into a tared capsule, where it was allowed to evaporate
spontaneously. A second and third portion of ether, each of 50 c.c., were
used in the same way, and the whole evaporated to dryness in the capsule.
A scanty, greenish, oily residue was left in the capsule, in which there
was no appearance of a crystallized alkaloid. The capsule and contents
were then weighed and the weight noted. The oily residue was then
repeatedly washed with small quantities of water, until the washings no
longer affected litmus-paper. The oily matter adhered to the capsule
during this process, no part of it coming off with the washing, and at
the end of the washing the capsule and contents were again dried and
weighed, and the weight subtracted from the original weight. The
difference was taken as the alkaloid cocaine, and it amounted to 0.077
grm., equal to 0.26 per cent.
Several preliminary assays were made in reaching this method. Some
authorities recommend the very finely powdered mixture of coca and
magnesia, or coca and lime, to be at once exhausted with ether. Others
recommend that the mixture be made into a paste with water, and after
drying on a water-bath that it be then exhausted with ether. This is
better, but neither of these methods were satisfactory.
Finally, 30 c.c. of a well made fluid extract of the same coca was
thoroughly mixed with 8 grms. of caustic magnesia in a capsule, and the
mixture dried on a water-bath and powdered. This powder was then
exhausted, one part by ether and the other part by chloroform, exactly as
in the method given, both parts giving very slightly higher results. As a
check upon the results, the solution of alkaloid washed out was titrated
with normal solution of oxalic acid.
From all this it would appear that this inferior coca of the markets, or
rather the best that can be selected from it, yields about the same
proportion of the alkaloid as was obtained by Niemann and Maisch, but it
has been shown that, by the older processes of assay used by them, much
of the alkaloid was probably lost or destroyed, and that much better
results are generally obtained by the modern process.
Now, since 3 drachms of this coca, or three fluid drachms of its fluid
extract, gave the same physiological, or perhaps therapeutical, effect as
3 grains of caffeine, and as the 3 drachms contained about 0.45 grain of
cocaine, it follows that cocaine is about 6.5 times more effective than
caffeine; but it also follows that the coca accessible, and even the very
best coca, contains very much less of its alkaloid than those articles
which yield caffeine do of that principle.
* * * * *
THE MELLOCO.
ULLUCUS TUBEROSA.--Early last year two tubers of this plant were received
at Kew from Caracas, and from out of doors in a prepared bed in June. The
result of this experiment, together with a few particulars as to the
esculent properties of the tubers, may be worth recording, as I believe
several gardeners, among them being the Messrs. Sutton, have obtained
tubers of the Ullucus from Kew with a view to giving it a trial. The two
Caracas tubers mentioned above were as large as hens' eggs, rather
longer, and somewhat flattened; the skin was red, as in some potatoes.
These, when placed in heat, rapidly developed shoots, which were removed
as soon as they were strong enough to form cuttings; in this way about a
hundred sturdy young plants were obtained and made ready for planting out
of doors in June. They were planted in a light, sandy, well manured soil
in a position exposed to full sunshine. Here they grew quickly, forming
by the middle of August tufts of shoots and leaves one foot across. They
were earthed up as for potatoes, and the strongest shoots were pegged
down and partly covered with soil, though the latter proved unnecessary.
At this time there were no tubers nor any signs of them. On again
examining the plants in September (about the middle), we were surprised
to find no tubers had yet been formed. The plants were now very strong,
and it was therefore concluded that instead of forming tubers the
strength of the plants had "run to leaves." We gave them up, no further
notice being taken of them till the frost came, when on perceiving that a
frost of four or five degrees did not injure the foliage, we again
examined the plants, and found an abundant crop of tubers just below the
surface of the soil, and varying in size from that of peas to pigeons'
eggs. The plants were left till the haulms had been destroyed by cold,
after which the tubers were gathered. On cooking some of the larger ones
by boiling for half an hour, we found them still rather hard, and with a
flavor of potatoes, almost concealed under a strong earthy taste, quite
disagreeable and soap-like. Considering how short a time these tubers had
had to grow in it is not improbable that their hardness and disagreeable
taste were owing to their being unripe; no doubt young, green potatoes
(these Ullucus tubers were partly green) would be quite as nauseous as
these were.
[Illustration: MELLOCO TUBERS.]
We are told that the Ullucus is extensively cultivated in Peru and
Bolivia, in the elevated regions where the common potato also thrives,
and with which the Ullucus is equally popular as a tuber-yielding plant.
In the _Gardeners' Chronicle_ for 1848, p. 862, Mr. J.B. Pentland stated
that the Ullucus "is planted in July or August, the seed employed being
generally the smaller tubers, unfit for food, and is gathered in during
the last week of April. These two periods of the year are the spring and
autumn in the southern hemisphere. The mode of cultivation is in drills,
into which the root is dropped, with a little manure. The climate, even
during the summer season, is severe, scarcely a night passing over
without the streams being frozen over, the sky being in general cloudless
at all periods of the year except during the rainy season (December to
March). Mean temperature about 49 deg.." This information seems to support
the view formed of this plant from its behavior at Kew last year, namely,
that the tubers are formed on the approach of cold weather, and that, so
long as the weather is warm and bright, leaves only are developed. Plants
grown in houses where the temperature has not been allowed to fall below
50 deg. in winter did not form any tubers, although they were in good health.
We found no tubers on the plants grown out of doors till some time after
the return of cold, wet weather. It seems likely that this plant does not
develop tubers unless its existence is threatened by cold; at all events,
such a conclusion seems reasonable from the above statements.
Possibly a wet and rather cold autumn would be favorable to this plant
and the production of its tubers--such a season, for instance, as would
be most unfavorable for the common potato. It would be worth while
testing the Ullucus for low and cold situations where the potato would
not thrive. There is not much probability of the former ever proving a
substitute for or even a rival to the potato, at least in this country;
but there is room for another good esculent, and the Ullucus is prolific
enough, hardy enough, and, we suppose, when properly grown, palatable
enough to be worthy a trial. In the _Gardeners' Chronicle_ for 1848, p.
828, will be found a most interesting detailed account of experiments
made with this plant in France by M. Louis Vilmorin.--_W. Waston, Kew;
The Gardeners' Chronicle_.
* * * * *
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