Scientific American Supplement, No. 303
by
Various
Part 2 out of 3
by me is 1.78 mm.; its length above the bends (U, Figure 2) is 310 mm.;
below the bends the length is 815 mm. The bends constitute a fluid valve
that prevents the air from returning into the pump; beside this, the
play of the mercury in them greatly facilitates the passage of the
air downward. The top of the mercury column representing the existing
barometric pressure should be about 25 mm. below the bends when the pump
is in action. This is easily regulated by an adjustable shelf, which is
also employed to fill the bends with mercury when a measurement is taken
or when the pump is at rest. On the shelf is a tube, 160 mm. high and 20
mm. in diameter, into which the end of the fall-tube dips; its side has
a circular perforation into which fits a small cork with a little tube
bent at right angles. With the hard end of a file and a few drops of
turpentine the perforation can be easily made and shaped in a few
minutes. By revolving the little bent tube through 180 deg. the flow of the
mercury can be temporarily suspended when it is desirable to change the
vessel that catches it.
_Gauge_.--For the purpose of measuring the vacua I have used an
arrangement similar to McLeod's gauge, Figure 4; it has, however, some
peculiarities. The tube destined to contain the compressed air has a
diameter of 1.35 mm. as ascertained by a compound microscope; it is not
fused at its upper extremity, but closed by a fine glass rod that fits
into it as accurately as may be, the end of the rod being ground flat
and true. This rod is introduced into the tube, and while the latter
is gently heated a very small portion of the cement described below is
allowed to enter by capillary attraction, but not to extend beyond the
end of the rod, the operation being watched by a lens. The rod is
used for the purpose of obtaining the compressed air in the form of a
cylinder, and also to allow cleansing of the tube when necessary. The
capacity of the gauge-sphere was obtained by filling it with mercury;
its external diameter was sixty millimeters; for measuring very high
vacua this is somewhat small and makes the probable errors rather
large; I would advise the use of a gauge-sphere of about twice as great
capacity. The tube, CB, Figure 4, has the same bore as the measuring
tube in order to avoid corrections for capillarity. The tube of the
gauge, CD, is not connected with an India-rubber tube, as is usual,
but dips into mercury contained in a cylinder 340 mm. high, 58 mm. in
diameter, which can be raised and lowered at pleasure. This is best
accomplished by the use of a set of boxes of various thicknesses, made
for the purpose and supplemented by several sheets of cardboard and even
of writing-paper. These have been found to answer well and enable the
experimenter to graduate with a nicety the pressure to which the gas is
exposed during measurement. By employing a cylinder filled with mercury
instead of the usual caoutchouc tubing small bubbles of air are
prevented from entering the gauge along with the mercury. An adjustable
brace or support is used which prevents accident to the cylinder when
the pump is inclined for the purpose of pumping out the vacuum-bulb. The
maximum pressure that can be employed in the gauge used by me is 100 mm.
All the tubing of the pump is supported at a distance of about 55 mm.
from the wood-work; this is effected by the use of simple adjustable
supports and adjustable clamps; the latter have proved a great
convenience. The object is to gain the ability to heat with a Bunsen
burner all parts of the pump without burning the wood-work. Where glass
and wood necessarily come in contact the wood is protected by metal or
simply painted with a saturated solution of alum. The glass portions
of the pump I have contrived to anneal completely by the simple means
mentioned below. If the glass is not annealed it is certain to crack
when subjected to heat, thus causing vexation and loss of time. The
mercury was purified by the same method that was used by W. Siemens
(Pogg. Annalen, vol. ex., p. 20), that is, by a little strong sulphuric
acid to which a few drops of nitric acid had been added; it was dried by
pouring it repeatedly from one hot dry vessel to another, by filtering
it while quite warm, the drying being completed finally by the action of
the pump itself. All the measurements were made by a fine cathetometer
which was constructed for me by William Grunow; see this Journal, Jan.,
1874, p. 23. It was provided with a well-corrected object-glass having a
focal length of 200 mm. and as used by me gave a magnifying power of 16
diameters.
_Manipulation_.--The necessary connections are effected with a cement
made by melting Burgundy pitch with three or four per cent of gutta
percha. It is indispensable that the cement when cold should be so hard
as completely to resist taking any impression from the finger nail,
otherwise it is certain to yield gradually and finally to give rise to
leaks. The connecting tubes are selected so as to fit as closely as
possible, and after being put into position are heated to the proper
amount, when the edges are touched with a fragment of cold cement which
enters by capillary attraction and forms a transparent joint that can
from time to time be examined with a lens for the colors of thin plates,
which always precede a leak. Joints of this kind have been in use by me
for two months at a time without showing a trace of leakage, and the
evidence gathered in another series of unfinished experiments goes to
show that no appreciable amount of vapor is furnished by the resinous
compound, which, I may add, is never used until it has been repeatedly
melted. As drying material I prefer caustic potash that has been in
fusion just before its introduction into the drying tube; during the
process of exhaustion it can from time to time be heated nearly to the
melting point: if actually fused in the drying tube the latter almost
invariably cracks. The pump in the first instance is to be inclined at
an angle of about 10 degrees, the tube of the gauge being supported by
a semicircular piece of thick pasteboard fitted with two corks into the
top of the cylinder. This seemingly awkward proceeding has in no case
been attended with the slightest accident, and owing to the presence of
the four leveling-screws, the pump when righted returns, as shown by the
telescope of the cathetometer, almost exactly to its original place. In
the inclined position the exhaustion of the vacuum bulb is accomplished
along with that of the rest of the pump. The exhaustion of the
vacuum-bulb when once effected can be preserved to a great extent for
use in future work, merely by allowing mercury from the reservoir to
flow in a rapid stream at the time that air is allowed to re-enter the
pump. During the first process of exhaustion the tube of the gauge is
kept hot by moving to and fro a Bunsen burner, and is in this way
freed from those portions of air and moisture that are not too firmly
attached. After a time the vacuum-bulb ceases to deliver bubbles of
air; it and the attached tube are now to be heated with a moving Bunsen
burner, when it will be found to furnish for 15 or 20 minutes a large
quantity of bubbles mainly of vapor of water. After then production
ceases the pump is righted and the exhaustion carried farther. In spite
of a couple of careful experiments with the cathetometer I have not
succeeded in measuring the vacuum in the vacuum bulb, but judge from
indications, that is about as high as that obtained in an ordinary
Geissler pump. Meanwhile the various parts of the pump can be heated
with a moving Bunsen burner to detach air and moisture, the cement being
protected by wet lamp-wicking. In one experiment I measured the amount
of air that was detached from the walls of the pump by heating them for
ten minutes somewhat above l00 deg. C., and found that it was 1/1,000,000
of the air originally present. I have also noticed that a still larger
amount of air is detached by electric discharges. This coincides with an
observation of E. Bessel-Hagen in his interesting article on a new form
of Toepler's mercury-pump (Annalen der Physik und Chemie, 1881, vol.
xii.). Even when potash is used a small amount of moisture always
collects in the bends of the fall tube; this is readily removed by a
Bunsen burner; the tension of the vapor being greatly increased, it
passes far down the fall-tube in large bubbles and is condensed. Without
this precaution I have found it impossible to obtain a vacuum higher
than 1/25,000,000; in point of fact the bends should always be heated
when a high exhaustion is undertaken even if the pump has been standing
well exhausted for a week; the heat should of course never be applied at
a late stage of the exhaustion. Conversely, I have often by the aid of
heat completely and quickly removed quite large quantities of the vapor
of water that had been purposely introduced. The exhaustion of the
vacuum-bulb is of course somewhat injured by the act of using the pump
and also by standing for several days, so that it has been usual with me
before undertaking a high exhaustion to incline the pump and re-exhaust
for 20 minutes; I have, however, obtained very high vacua without using
this precaution.
During the process of exhaustion not more than one-half of the mercury
in the reservoir is allowed to run out, other wise when it is returned
bubbles of air are apt to find their way into the vacuum-bulb. In order
to secure its quiet entrance it is poured into a silk bag provided with
several holes. When the reservoir is first filled its walls for a day
or two appear to furnish air that enters the vacuum-bulb; this action,
however, soon sinks to a minimum and then the leakage remains quite
constant for months together.
_Measurement of the vacuum_.--The cylinder into which the gauge-tube
dips is first elevated by a box sufficiently thick merely to close the
gauge, afterwards boxes are placed under it sufficient to elevate the
mercury to the base of the measuring tube; when the mercury has reached
this point, thin boards and card-boards are added till a suitable
pressure is obtained. The length of the inclosed cylinder of air is
then measured with the cathetometer, also the height of the mercurial
"meniscus," and the difference of the heights of the mercurial columns
in A and B, figure 4. To obtain a second measure an assistant removes
some of the boxes and the cylinder is lowered by hand three or four
centimeters and then replaced in its original position. In measuring
really high vacua, it is well to begin with this process of lowering and
raising the cylinder, and to repeat it five or six times before taking
readings. It seems as though the mercury in the tube, B, supplies to the
glass a coating of air that allows it to move more freely; at all events
it is certain that ordinarily the readings of B become regular, only
after the mercury has been allowed to play up and down the tube a number
of times. This applies particularly to vacua as high 1/50,000,000 and to
pressures of five millimeters and under. It is advantageous in making
measurements to employ large pressures and small volumes; the correct
working of the gauge can from time to time be tested by varying the
relations of these to each other. This I did quite elaborately, and
proved that such constant errors as exist are small compared with
inevitable accidental errors, as, for example, that there was no
measurable correction for capillarity, that the calculated volume of the
"meniscus" was correct, etc. It is essential in making a measurement
that the temperature of the room should change as little as possible,
and that the temperature of the mercury in the cylinder should be at
least nearly that of the air near the gauge-sphere. The computation is
made as follows
n = height of the cylinder inclosing the air;
c = a factor which, multiplied by n, converts it into cubic
millimeters;
S = cubic contents of the meniscus;
d = difference of level between A and B, fig. 4;
= the pressure the air is under;
N = the cubic contents of the gauge in millimeters;
x = a fraction expressing the degree of exhaustion obtained; then
x=1/([N (760/d)]/[nc - S])
It will be noticed that the measurements are independent of the actual
height of the barometer, and if several readings are taken continuously,
the result will not be sensibly affected by a simultaneous change of the
barometer. Almost all the readings were taken at a temperature of about
20 deg. C., and in the present state of the work corrections for temperature
may be considered a superfluous refinement.
_Gauge correction_.--It is necessary to apply to the results thus
obtained a correction which becomes very important when high vacua are
measured. It was found in an early stage of the experiments that the
mercury, in the act of entering the highly exhausted gauge, gave out
invariably a certain amount of air which of course was measured along
with the residuum that properly belonged there; hence to obtain the true
vacuum it is necessary to subtract the volume of this air from nc. By a
series of experiments I ascertained that the amount of air introduced by
the mercury in the acts of entering and leaving the gauge was sensibly
constant for six of these single operations (or for three of these
double operations), when they followed each other immediately. The
correction accordingly is made as follows: the vacuum is first measured
as described above, then by withdrawing all the boxes except the lowest,
the mercury is allowed to fall so as nearly to empty the gauge; it is
then made again to fill the gauge, and these operations are repeated
until they amount in all to six; finally the volume and pressure are a
second time measured. Assuming the pressure to remain constant, or that
the volumes are reduced to the same pressure,
v = the original volume; v' = the final volume;
V' = volume of air introduced by the first entry of the mercury;
V = corrected volume; then
V' = (v'-v)/6
V = v - [(v'-v)/6]
It will be noticed that it is assumed in this formula that the same
amount of air is introduced into the gauge in the acts of entry and
exit; in the act of entering in point of fact more fresh mercury is
exposed to the action of the vacuum than in the act exit, which might
possibly make the true gauge-correction rather larger than that given by
the formula. It has been found that when the pump is in constant use the
gauge-correction gradually diminishes from day to day; in other words,
the air is gradually pumped out of the gauge-mercury. Thus on December
21, the amount of air entering with the mercury corresponded to an
exhaustion of
1/27,308,805 .......Dec. 21.
1/38,806,688 ...... Dec. 29.
1/78,125,000 .......Jan. 15.
1/83,333,333 .......Jan. 23
1/128,834,063 ......Feb. 1.
1/226,757,400 ..... Feb. 9.
1/232,828,800 ..... Feb. 19.
1/388,200,000 ......March 7.
That this diminution is not due to the air being gradually withdrawn
from the walls of the gauge or from the gauge-tube, is shown by the fact
that during its progress the pump was several times taken to pieces, and
the portions in question exposed to the atmosphere without affecting
the nature or extent of the change that was going on. I also made one
experiment which proves that the gauge-correction does not increase
sensibly, when the exhausted pump and gauge are allowed to stand unused
for twenty days.
_Rate of the pump's work_.--It is quite important to know the rate of
the pump at different degrees of exhaustion, for the purpose of enabling
the experimenter to produce a definite exhaustion with facility; also if
its maximum rate is known and the minimum rate of leakage, it becomes
possible to calculate the highest vacuum attainable with the instrument.
Examples are given in the tables below; the total capacity was about
100,000 cubic mm.
Time. Exhaustion. Ratio.
1/78,511
10 minutes }........ 1:1/3.53
1/276,980
10 minutes }........ 1:1/6.10
1/1,687,140
10 minutes }........ 1:1/4.15
1/7,002,000
Upon another occasion the following rates and exhaustions were obtained:
Time. Exhaustion. Rate.
1/7,812,500
10 minutes }........ 1:1/3.18
1/24,875,620
10 minutes }........ 1:1/2.69
1/67,024,090
10 minutes }........ 1:1/1.22
1/81,760,810
10 minutes }........ 1:1.67
1/136,986,300
10 minutes }........ 1:1.23
1/170,648,500
The _irregular_ variations in the rates are due to the mode in which the
flow of the mercury was in each case regulated.
_Leakage_.--We come now to one of the most important elements in the
production of high vacua. After the air is detached from the walls of
the pump the leakage becomes and remains nearly constant. I give below a
table of leakages, the pump being in each case in a condition suitable
for the production of a very high vacuum:
Duration of the Leakage per hour in
experiment cubic mm., press.,
760 mm.
181/2 hours............................ 0.000853
27 hours............................ 0.001565
261/2 hours.............................0.000791
20 hours.............................0.000842
19 hours.............................0.000951
19 hours.............................0.001857
7 days..............................0.001700
7 days..............................0.001574
Average.................... 0.001266
I endeavored to locate this leakage, and proved that one-quarter of
it is due to air that enters the gauge from the top of its column of
mercury, thus:
Duration of the Gauge-leakage per hour
experiment. in cubic mm., press.
760 mm.
18 hours.................................0.0002299
7 days..................................0.0004093
7 days..................................0.0003464
Average.......................0.0003285
This renders it very probable that the remaining three quarters are due
to air given off from the mercury at B, Fig. 4, from that in the bends
and at the entrance of the fall-tube, _o_, Fig. 3.
Further on some evidence will be given that renders it probable that the
leakage of the pump when in action is about four times as great as the
total leakage in a state of rest.
The gauge, when arranged for measurement of gauge-leakage, really
constitutes a barometer, and a calculation shows that the leakage would
amount to 2.877 cubic millimeters per year, press. 760 mm. If this air
were contained in a cylinder 90 mm. long and 15 mm. in diameter it would
exert a pressure of 0.14 mm. To this I may add that in one experiment
I allowed the gauge for seven days to remain completely filled with
mercury and then measured the leakage into it. This was such as would
in a year amount to 0.488 cubic millimeter, press. 760 mm., and in a
cylinder of the above dimensions would exert a pressure of 0.0233 mm.
_Reliability of the results: highest vacuum._
The following are samples of the results obtained. In one case sixteen
readings were taken in groups of four with the following result:
Exhaustion.
1 / 74,219,139
1 / 78,533,454
1 / 79,017,272
1 / 68,503,182
Mean 1 / 74,853,449
Calculating the probable error of the mean with reference to the above
four results it is found to be 2.28 per cent of the quantity involved.
A higher vacuum measured in the same way gave the following results:
1 / 146,198,800
1 / 175,131,300
1 / 204,081,600
1 / 201,207,200
The mean is 1 / 178,411,934, with a probable error of 5.42 per cent of
the quantity involved. I give now an extreme case; only five single
readings were taken; these corresponded to the following exhaustions:
1 / 379,219,500
1 / 371,057,265
1 / 250,941,040
1 / 424,088,232
1 / 691,082,540
The mean value is 1 / 381,100,000, with a probable error of 10.36 per
cent of the quantity involved. Upon other occasions I have obtained
exhaustions of 1 / 373,134,000 and 1 / 388,200,000. Of course in these
cases a gauge-correction was applied; the highest vacuum that I have
ever obtained irrespective of a gauge-correction was 1 / 190,392,150. In
these cases and in general, potash was employed as the drying material;
I have found it practical, however, to attain vacua as high as 1 /
50,000,000 in the total absence of all such substances. The vapor of
water which collects in bends must be removed from time to time with a
Bunsen burner while the pump is in action.
It is evident that the final condition of the pump is reached when
as much air leaks in per unit of time as can be removed in the same
interval. The total average leakage per ten minutes in the pump used by
me, when at rest, was 0.000211 cubic millimeter at press. 760 mm. Let
us assume that the leakage when the pump is in action is four times
as great as when at rest; then in each ten minutes 0.000844 cubic
millimeter press., 760 mm., would enter; this corresponds in the pump
used by me to an exhaustion of 1 / 124,000,000; if the rate of the pump
is such as to remove one-half of the air present in ten minutes, then
the highest attainable exhaustion would be 1 / 248,000,000. In the same
way it may be shown that if six minutes are required for the removal of
half the air the highest vacuum would be 1 / 413,000,000 nearly, and
rates even higher than this have been observed in my experiments. An
arrangement of the vacuum-bulb whereby the entering drops of mercury
would be exposed to the vacuum in an isolated condition for a somewhat
longer time would doubtless enable the experimenter to obtain
considerably higher vacua than those above given.
_Exhaustion obtained with a plain Sprengel Pump._--I made a series of
experiments with a plain Sprengel pump without stopcocks, and arranged,
as far as possible, like the instrument just described. The leakage per
hour was as follows:
Duration of the Leakage per hour in
experiment. cubic mm. at press.
760 mm.
22 hours 0.04563
2 days 0.04520
2 days 0.09210
4 days 0.06428
-------
Mean 0.06180
Using the same reasoning as above we obtain the following table
Time necessary for removal Greatest attainable
of half the air. exhaustion.
10 minutes 1 / 5,000,000
7.5 minutes 1 / 7,000,000
6.6 minutes 1 / 12,000,000
In point of fact the highest exhaustion I ever obtained with this pump
was 1 / 5,000,000; from which I infer that the leakage during action
is considerably greater than four times that of the pump at rest. The
general run of the experiments tends to show that the leakage of a plain
Sprengel pump, without stopcocks or grease, is, when in action, about 80
times as great as in the form used by me.
_Note on annealing glass tubes._--It is quite necessary to anneal all
those parts of the pump that are to be exposed to heat, otherwise they
soon crack. I found by inclosing the glass in heavy iron tubes and
exposing it for five hours to a temperature somewhat above that of
melting zinc, and then allowing an hour or two for the cooling process,
that the strong polarization figure which it displays in a polariscope
was completely removed, and hence the glass annealed. A common
gas-combustion furnace was used, the bends, etc, being suitably inclosed
in heavy metal and heated over a common ten-fold Bunsen burner. Thus far
no accident has happened to the annealed glass, even when cold drops of
mercury struck in rapid succession on portions heated considerably above
100 deg. C.
I wish, in conclusion, to express my thanks to my assistant, Dr.
Ihlseng, for the labor he has expended in making the large number of
computations necessarily involved in work of this kind.--_Amer. Jour. of
Science._
* * * * *
CRYSTALLIZATION TABLE.
The following table, prepared by E. Finot and Arm. Bertrand for the
_Jour. de Ph. et de Chim._, shows the point at which the evaporation of
certain solutions is to be interrupted in order to procure a good crop
of crystals on cooling. The density is according to Baume's scale, the
solution warm:
Aluminum sulphate 25 | Nickel acetate 30
Alum (amm. or pot.) 20 | " ammon. sulphate 18
Ammonium acetate 14 | " chloride 50
" arsenate 5 | " sulphate 40
" benzoate 5 | Oxalic acid 12
" bichromate 28 | Potass. and sod. tartrate 36
" bromide 30 | Potassium arsenate 36
" chloride 12 | " benzoate 2
" nitrate 29 | " bisulphate 35
" oxalate 5 | " bromide 40
" phosphate 35 | " chlorate 22
" sulphate 28 | " chloride 25
" sulphocyanide 18 | " chromate 38
" tartrate 25 | " citrate 36
Barium ethylsulphate 43 | " ferrocyanide 38
" formate 32 | " iodide 17
" hyposulphite 24 | " nitrate 28
" nitrate 18 | " oxalate 30
" oxide 12 | " permanganate 25
Bismuth nitrate 70 | " sulphate 15
Boric acid 6 | " sulphite 25
Cadmium bromide 65 | " sulphocyanide 35
Calcium chloride 40 | " tartrate 48
" ethylsulphate 36 | Soda 28
" lactate 8 | Sodium acetate 22
" nitrate 55 | " ammon. phosp. 17
Cobalt chloride 41 | " arsenate 36
" nitrate 50 | " borate 24
" sulphate 40 | " bromide 55
Copper acetate 5 | " chlorate 43
" ammon. sulph. 35 | " chromate 45
" chloride 45 | " citrate 36
" nitrate 55 | " ethylsulphate 37
" sulphate 30 | " hyposulphite 24
Iron-ammon. oxalate 30 | " nitrate 40
" ammon. sulphate 31 | " phosphate 20
" sulphate 31 | " pyrophosphate 18
" tartrate 40 | " sulphate 30
Lead acetate 42 | " tungstate 45
" nitrate 50 | Stroutium bromide 50
Magnesium chloride 35 | " chlorate 65
" lactate 6 | " chloride 34
" nitrate 45 | Tin choride (stannous) 75
" sulphate 40 |
Manganese chloride 47 | Zinc acetate 20
" lactate 8 | " ammon. chloride 43
" sulphate 44 | " nitrate 55
Mercury cyanide 20 | " sulphate 45
* * * * *
THE PRINCIPLES OF HOP-ANALYSIS.
By Dr. G. O. CECH
[Footnote: 'Zeitschrift fur Analyt. Chemie,' 1881.]
Hop flowers contain a great variety of different substances susceptible
of extraction with ether, alcohol, and water, and distinguishable from
one another by tests of a more or less complex character. The substances
are: Ethereal oil, chlorophyl, hop tannin, phlobaphen, a wax-like
substance, the sulphate, ammoniate, phosphate, citrate and malates of
potash, arabine, a crystallized white and an amorphous brown resin, and
a bitter principle. That the characteristic action of the hops is due to
such of these constituents only as are of an organic nature is easy to
understand; but up to the present we are in ignorance whether it is upon
the oil, the wax, the resin, the tannin, the phlobaphen, or the bitter
principle individually, or upon them all collectively, that the effect
of the hops in brewing depends.
It is the rule to judge the strength and goodness of hops by the amount
of farina--the so-called lupuline; and as this contains the major
portion of the active constituents of the hop, there is no doubt that
approximately the amount of lupuline is a useful quantitative test. But
here we are confronted by the question whether the lupuline is to be
regarded as containing _all_ that is of any value in the hops and the
leaves, the organic principles in which pass undetected under such a
test, as supererogatory for brewers' purposes? Practical experience
negatives any such conclusion. Consequently, we are justified in
assuming that the concurrent development and the presence of the several
organic principles--the oil, the wax, the bitter, the tannin, the
phlobaphen, in the choicer sorts--are subject, within certain limits, to
variations depending on skilled culture and careful drying, and that the
aggregate of these principles has a certain attainable maximum in
the finer sorts, under the most favorable conditions of culture, and
another, lower maximum in less perfectly cultivated and wild sorts. The
difference in the proportion of active organic substance in each sort
must be determined by analysis. There then remains to be discovered
which of the aforesaid substances plays the leading role in brewing, and
also whether the presence of chlorophyl and inorganic salts in the hop
extract influences or alters the results.
That in brewing hops cannot be replaced by lupuline alone, even when the
latter is employed in relatively large quantities is well known, as also
that a considerable portion of the bitter principle of the hop is found
in the floral leaves. Neither can the lupuline be regarded as the only
active beer agent, as both the hop-tannin and the hop-resin serve to
precipitate the albuminous matter, and clarify and preserve the beer.
Both chemists and brewers would gladly welcome some method of testing
hops, which should be expeditious, and afford reliable results in
practical hands. To accomplish this account must be taken of all the
active organic constituents of the hops, which can be extracted either
with ether, alcohol, or water containing soda (for the conversion of the
hop tannin in phlobaphen).[1] It should further be ascertained whether
the chlorophyl percentage in the hop bells, new and old, is or is not
the same in cultivated and in wild hops, and whether the aggregate
percentages of organic and constituent observe the same limits.
[Footnote 1: See C. Etti, in "Dingler's Polytech. Journ.," 1878, p.
354.]
As wild hops nowadays are frequently introduced in brewing, the
proportion of chlorophyl and organic and inorganic constituents in them
should be compared with those of cultivated sorts, taking the best
Bavarian or Bohemian hops as the standard of measurement. The chlorophyl
is of minor importance, as it has little effect on the general results.
By a series of comparative analysis of cultivated and wild hops, in
which I would lay especial stress on parity of conditions in regard
of age and vegetation, the extreme limits of variation of which their
active organic principles are susceptible could be determined.
There is every reason to suppose that the chlorophyl and inorganic
constituents do not differ materially in the most widely different sorts
of hops. The more important differences lie in the proportions of hop
resin and tannin. When this is decided, the proportion of tannin or
phlobaphen in the hop extract or the beer can be determined by analysis
in the ordinary way. But whenever some quick and sure hop test shall
have been found, _appearance and aroma_ will still be most important
factors in any estimate of the value of hops. Here a question arises as
to whether hops from a warm or even a steppe climate, like that of
South Russia, contain the same proportion of ethereal oil--that is, of
aroma--as those from a cooler climate, like Bavaria and Bohemia, or
like certain other fruit species of southern growth, they are early
in maturing, prolific, large in size, and abounding in farina, but
_deficient in aroma_.
The bearings of certain experimental data on this point I reserve for
consideration upon a future occasion.--_The Analyst_.
* * * * *
WATER GAS.
A DESCRIPTION OF APPARATUS FOR PRODUCING CHEAP GAS, AND SOME NOTES ON
THE ECONOMICAL EFFECT OF USING SUCH GAS WITH GAS MOTORS, ETC.
[Footnote: Abstract of paper read in Section G. British Association,
York]
By MR. J. EMERSON DOWSON, C.E., of London.
In many countries and for many years past, inventors have sought
some cheap and easy means of decomposing steam in the presence of
incandescent carbon in order to produce a cheap heating gas; and working
with the same object the writer has devised an apparatus which has been
fitted up in the garden of the Industrial Exhibition, and is there
making gas for a 31/2 horse power (nominal) Otto gas engine. The retort or
generator consists of a vertical cylindrical iron casing which incloses
a thick lining of ganister to prevent loss of heat and oxidation of the
metal, and at the bottom of this cylinder is a grate on which a fire is
built up. Under the grate is a closed chamber, and a jet of superheated
steam plays into this and carries with it by induction a continuous
current of air. The pressure of the steam forces the mixture of steam
and air upward through the fire, so that the combustion of the fuel is
maintained while a continuous current of steam is decomposed, and in
this way the working of the generator is constant, and the gas is
produced without fluctuations in quality. The well-known reactions
occur, the steam is decomposed, and the oxygen from the steam and air
combines with the carbon of the fuel to form carbon dioxide (CO_2),
which is reduced to the monoxide (CO) on ascending the fuel column.
In this way the resulting gases form a mixture of hydrogen, carbon,
monoxide, and nitrogen, with a small percentage of carbon dioxide which
usually escapes without reduction. The steam should have a pressure of
11/2 to 2 atmospheres, and is produced and superheated in a zigzag coil
fed with water from a neighboring boiler. The quantity of water required
is very small, being only about 7 pints for each 1,000 cubic feet of
gas, and, except on the first occasion when the apparatus is started,
the coil is heated by some of the gas drawn from the holder, so that
after the gas is lighted under the coil the superheater requires no
attention.
For boiler and furnace work the gas can be used direct from the
generator; but where uniformity of pressure is essential, as for gas
engines, gas burners, etc., the gas should pass into a holder. The
latter somewhat retards the production, but the steam injector causes
gas to be made so rapidly that a holder is easily filled against a back
pressure of 1 in. to 11/2 in. of water, and at this pressure the generator
can pass gas continuously into the holder, while at the same time it is
being drawn off for consumption.
The nature of the fuel required depends on the purpose for which the gas
is used. If for heating boilers, furnaces, etc, coke or any kind of coal
maybe used; but for gas engines or any application of the gas requiring
great cleanliness and freedom from sulphur and ammonia it is best to use
anthracite, as this does not yield condensable vapors, and is very free
from impurities. Good qualities of this fuel contain over 90 per cent of
carbon and so little sulphur that, for some purposes, purification is
not necessary. For gas engines, etc., it is, however, better to pass
the gas through some hydrated oxide of iron to remove the sulphureted
hydrogen. The oxide can be used over and over again after exposure to
the air, and the purifying is thus effected without smell or appreciable
expense. Gas made by this process and with anthracite coal has no tar
and no ammonia, and the small percentage of carbon dioxide present does
not sensibly affect the heating power. A further advantage of this gas
is that it cannot burn with a smoky flame, and there is no deposition of
soot even when the object to be heated is placed over or in the flame,
and this is of importance for the cylinder and valves of a gas engine.
To produce 1,000 cubic feet only 12 lb. of anthracite are required,
allowing 8 to 10 per cent, for impurities and waste; thus a generator
A size, which produces 1,000 cubic feet per hour, needs only 12 lb. in
that time, and this can be added once an hour or at longer intervals. No
skilled labor is necessary, and in practice it is usual to employ a man
who has other work to attend to near the generator, and to pay him a
small addition to his usual wages.
The comparative explosive force of coal gas and the Dowson gas
calculated in the usual way is as 3.4:1, i. e., coal gas has 3.4 times
more energy than the writer's gas. Messrs. Crossley, of Manchester, the
makers of the Otto gas engines, have made several careful trials of this
gas with some of their 31/2 horse power (nominal) engines, and in one
trial they took diagrams every half-hour for nine consecutive days.
These practical trials have shown that without altering the cylinder of
the engine it is possible to admit enough of the Dowson gas to give
the same power as with ordinary coal gas. It has been seen that the
comparative explosive force of the two gases is as 3.4:1, but as it is
well known the combustion of carbon monoxide proceeds at a comparatively
slow rate, and for this reason, and because of the diluents present in
the cylinder which affect the weaker gas more than coal gas, experience
has shown that it is best to allow five volumes of the Dowson gas for
one volume of coal gas, and then the same uniform power is obtained as
with the latter.
This gives very important economical results; for if the cost of the
Dowson gas given in the tables as 41/4d., 3-1/3d., and 23/4d. per 1,000
cubic feet, be multiplied by 5 there will be 1s. 91/4d., 1s. 43/4d., and 1s.
23/4d., or a mean of 1s. 51/2d. for the equivalent of 1,000 cubic feet of
coal gas, which usually costs from 3s. to 4s., and this represents an
actual saving of about 50 to 60 per cent, in working cost. Another
practical consideration is that coal gas requires 224 lb. to 250 lb. of
coal per 1,000 cubic feet of gas, but the writer requires only 12 lb.
per 1,000 cubic feet, and multiplying this by 5 to give the equivalent
of 1,000 cubic feet of coal gas, for engine work, there are 60 lb.
instead of 224 lb. to 250 lb. This is only 24 to 27 per cent, of the
weight of the coal required for coal gas, and in many outlying districts
this will effect an appreciable saving in the cost of transport.
APPENDIX.
TABLE I.
_Generator A Size_ (producing 1,000 cubic feet per hour):
Anthracite to make gas at the rate of 1,000 s. d.
cubic feet per hour=l2 lb x 9 working
hours=l08 lb., or say, 1 cwt. at 20s. a
ton.................................... 1 0
Allowance for wages of attendant......... 1 0
Repairs and depreciation of generator,
gasholder, etc. (5 per cent. on Ll25)=
per working day........................ 0 5
Interest on capital outlay, ditto........ 0 5
______
Total........................... 2 10
cub. ft.
Gas produced............................. 9.000
Less gas used for generating and
superheating steam..................... 1,000
_____
Total effective gas for 2s. 10d. 8,000
Net cost 41/4 d. per 1,000 cubic feet.
TABLE II.
_Generator B Size_ (producing 1,500 cubic feet per hour)
Anthracite to make gas at the rate of 1,500 s. d.
cubic feet per hour=18 lb. x 9 working
hours=162 lb., or, say, 11/2 cwt. 20s.
a ton.................................. 1 6
Allowance for wages of attendant......... 1 0
Repairs and depreciation of generator,
gasholder, etc. (5 per cent, on L140)
=per working day....................... 0 51/2
Interest on capital outlay, ditto........ 0 51/2
___ ___
Total........................... 3 5
cub. ft.
Gas produced............................. 13,500
Less gas used for generating and
superheating steam..................... 1,200
______
Total effective gas for 3s. 5d.. 12,300
Net cost 3 1/3d. per 1,000 cubic feet.
TABLE III.
_Generator C Size_ (producing 2,500 cubic feet per hour):
Anthracite to make gas at the rate of 2,500 s. d.
cubic feet per hour=30 lb. x 9 working
hours=270 lb. at 20s. a ton............ 2 41/2
Allowance for wages of attendant....... 1 6
Repairs and depreciation of generator,
gasholder, etc. (5 per cent, on L160)=
per working day...................... 0 61/2
Interest on capital outlay, ditto...... 0 61/2
_______
Total......................... 4 111/2
cub. ft.
Gas produced........................... 22,500
Less gas used for generating and
superheating steam................... 1,500
______
Total effective gas for 4s. 111/2d 21,000
Net cost, say, 23/4 d. per 1,000 cubic feet.
* * * * *
ON THE FLUID DENSITY OF CERTAIN METALS.
[Footnote: Abstract of paper read before Section C (Chemical Science),
British Association meeting, York.]
By PROFESSOR W. CHANDLER ROBERTS, F.R.S., and T. WRIGHTSON.
The authors described their experiments on the fluid density of metals
made in continuation of those submitted to Section B at the Swansea
meeting of the Association. Some time since one of the authors gave an
account of the results of experiments made to determine the density of
metallic silver, and of certain alloys of silver and copper when in a
molten state. The method adopted was that devised by Mr. R. Mallet, and
the details were as follows: A conical vessel of best thin Lowmoor plate
(1 millimeter thick), about 16 centimeters in height, and having an
internal volume of about 540 cubic centimeters, was weighed, first
empty, and subsequently when filled with distilled water at a known
temperature. The necessary data were thus afforded for accurately
determining its capacity at the temperature of the air. Molten silver
was then poured into it, the temperature at the time of pouring being
ascertained by the calorimetric method. The precautions, as regards
filling, pointed out by Mr. Mallet, were adopted; and as soon as the
metal was quite cold, the cone with its contents was again weighed.
Experiments were also made on the density of fluid bismuth; and two
distinctive determinations gave the following results:
10.005 )
) mean 10.039.
10.072 )
The invention of the oncosimeter, which was described by one of the
authors in the "Journal of the Iron and Steel Institute" (No. II.,
1879, p. 418), appeared to afford an opportunity for resuming the
investigation on a new basis, more especially as the delicacy of the
instrument had already been proved by experiments on a considerable
scale for determining the density of fluid cast iron. The following is
the principle on which this instrument acts:
If a spherical ball of any metal be plunged below the surface of a
molten bath of the same or another metal, the cold ball will displace
its own volume of molten metal. If the densities of the cold and molten
metal be the same, there will be equilibrium, and no floating or sinking
effect will be exhibited. If the density of the cold be greater than
that of the molten metal, there will be a sinking effect, and if less a
floating effect when first immersed. As the temperature of the submerged
ball rises, the volume of the displaced liquid will increase or decrease
according as the ball expands or contracts. In order to register these
changes the ball is hung on a spiral spring, and the slightest change in
buoyancy causes an elongation or contraction of this spring which can
be read off on a scale of ounces, and is recorded by a pencil on a
revolving drum. A diagram is thus traced out, the ordinates of which
represent increments of volume, or, in other words, of weight of fluid
displaced--the zero line, or line corresponding to a ball in a liquid of
equal density, being previously traced out by revolving the drum without
attaching the ball of metal itself to the spring, but with all other
auxiliary attachments. By means of a simple adjustment the ball is kept
constantly depressed to the same extent below the surface of the liquid;
and the ordinate of this pencil line, measuring from the line of
equilibrium, thus gives an exact measure of the floating or sinking
effect at every stage of temperature, from the cold solid to the state
when the ball begins to melt.
If the weight and specific gravity of the ball be taken when cold,
there are obtained, with the ordinate on the diagram at the moment of
immersion, sufficient data for determining the density of the fluid
metal; for
W / W1 = D / D1
the volumes being equal. And remembering that
W (weight of liquid) = W1 (weight of ball) + x
(where x is always measured as +_ve_ or -_ve_ floating effect), there is
obtained the equation:
D1 x ( W1 + x)
D = --------------- .
W1
[TEX: D = \frac{D_1 \times (W_1 +x)}{W_1}]
The results obtained with metallic silver are perhaps the most
interesting, mainly from the fact that the metal melts at a higher
temperature, which was determined with great care by the illustrious
physicist and metallurgist, the late Henri St. Claire Deville, whose
latest experiments led him to fix the melting point at 940 deg. Cent. The
authors of the paper showed that the density of the fluid metal was 9.51
as compared with 10.57, the density of the solid metal. Taking their
results generally, it is found that the change of volume of the
following metals in passing from the solid to the liquid state may be
thus stated:
Specific Specific
Metal. Gravity, Gravity, Percentage of
Solid. Liquid. Change.
Bismuth 9.82 10.055 Decrease of volume 2.3
Copper 8.8 8.217 Increase " 7.1
Lead 11.4 10.37 " " 9.93
Tin. 7.5 7.025 " " 6.76
Zinc 7.2 6.48 " " 11.10
Silver 10.57 9.51 " " 11.20
Iron 6.95 6.88 " " 1.02
* * * * *
HYDROPHOBIA PREVENTED BY VACCINATION.
M. Pasteur and other French savants have lately been devoting special
attention to hydrophobia. The great authority on germs has, in fact,
definitely announced that he does not intend to rest until he has made
known the exact nature and life-history of this terrible disease, and
discovered a means of preventing or curing it. The most curious result
yet attained in this direction, however, has been announced by Professor
V. Galtier, of the Lyons Veterinary School. This inquirer has found, in
the first place, that if the virus of rabies be injected into the veins
of a sheep, the animal does not subsequently exhibit any symptoms of
hydrophobia. This in itself would be a sufficiently curious result
to justify attention, though its importance, except as confirmatory
testimony, becomes less striking when it is remembered that M. Pasteur
has lately shown that the special _nidus_ of the disease appears to be
the nervous tissue, and particularly the ganglionic centers. But there
is this further curious consequence: sheep who have thus been treated
through the blood, and who are afterwards inoculated in the ordinary
way through the cellular tissue, as if by a bite, are proof against
the disease. It is as though the injection into the veins acted as a
vaccine. Twenty sheep were experimented upon; ten only were treated to
the venous injection, and then all were inoculated through the cellular
tissue. The ten which had been first "vaccinated" continue alive and
well; they have not even shown any adverse symptoms. The other ten have
all died of rabies. It remains to say why M. Galtier experimented
upon sheep, and not upon dogs and cats, which usually communicate the
disease. The incubation of the disease is much more rapid and less
capricious in the sheep than in the dog or in man, and hence M. Galtier
was able to get his results more certainly within a short period. Having
succeeded so far, he is now justified in undertaking the more protracted
series of observations which experiments upon the canine species will
involve; and this he proposes to do. Experiments of this nature are not
without a serious risk, and admiration is almost equally due to the
courage and the intelligence of the experimentalist. But what will the
anti-vaccinator say?--_Pall Mall Gazette_.
* * * * *
ON DIPTERA AS SPREADERS OF DISEASE.
By J.W. SLATER.
The two-winged flies, in their behavior to man, stand in a marked
contrast to all the other orders of insects. The Lepidoptera, the
Coleoptera, the Neuroptera, the Hymenoptera no doubt occasion, in some
of their forms at least, much damage to our crops. But none of them are
parasitic in or upon our bodies; none of them persistently intrude into
our dwellings, hover around us in our walks, and harass us with noise
and constant attempts to bite, or at least to crawl upon us. Even the
ants, except in a few tropical districts, rarely act upon the offensive.
The Hemiptera contain one semi-parasitic species which has attained a
"world-wide circulation," and one degraded, purely parasitic group.
But the Diptera, among which the fleas are now generally included as a
degenerated type, comprise more forms personally annoying to man than
all the remaining insect orders put together. These hostile species are,
further, incalculably numerous, and occur in every part of the globe.
Mosquitoes swarm not merely in the swampy forests of the Orinoco or the
Irrawaddy, but in the Tundras of Siberia, en the storm-beaten rocks of
the Loffodens, and are even encountered by voyagers in quest of the
North Pole. The common house fly was probably at one time peculiar to
the Eastern Continent, but it followed the footsteps of the Pilgrim
Fathers, and is now as great a nuisance in the United Slates and the
Dominion as in any part of Europe. It is curious, but distressing, to
note the tendency of evils to become international. We have communicated
to America the house-fly and the Hessian fly, the "cabbage-white,"
the small pox, and the cholera. She, in return, has given us the
_Phylloxera_, a few visitations of yellow fever, the _Blatta gigantea_,
and, climate allowing, may perhaps throw in the Colorado beetle as a
make-weight. In this department, at least, free trade reigns undisputed.
It is a singular thing that no beautiful, useful, or even harmless
species of bird or insect seems capable of acclimatizing itself as do
those characterized by ugliness and noisomeness.
But, returning from this digression, we find in the Diptera the habit of
obtrusion and intrusion, of coming in actual contact with our food and
our persons, combined with another propensity--that of feeding upon
carrion, excrement, blood, pus, and morbid matter of all kinds. This
is a combination far more serious than is generally imagined. If the
fly--which may at any moment settle upon our lips, our eyes, or upon
an abraded part of our skin--were cleanly in its habits, we need feel
little annoyance at its visits. Or if it were the most eager carrion
devourer, but did not, after having dined, think it necessary to
seek our company, we might hold it, as is done too hastily by some
naturalists, a valuable scavenger. I fear, however, that I have already
made too great a concession. So long as very many persons are suffering
from disease--so long as many diseases are capable of being transmitted
from the sick to the healthy--so long must any creature which is in the
habit of flying about, and touching first one person and then another,
be a possible medium of infection and death.
Let us take the following case, by no means imaginary, but a
generalization from occurrences far too frequent: A healthy man, sitting
in his house or walking in the fields, especially in countries where the
insectivorous birds have been shot down, suddenly feels a sharp prick on
his neck or his cheek. Putting his hand to the place he perhaps crushes,
perhaps merely brushes away, a fly which has bitten him so as to draw
blood. The man thinks little of so trifling a hurt, but the next morning
he finds the puncture exceedingly painful. An inflamed pimple forms,
which quickly gets worse, while constitutional symptoms of a feverish
kind come on. In alarm he seeks medical advice. The doctor tells him
that it is a malignant pustule, and takes at once the most active
measures. In spite of all possible skill and care the patient too often
succumbs to the bite of a _mouche charbonneuse_, or carbuncle-fly. But
has any kind of fly the property of producing malignant pustule by
some specific inherent power of its own? Surely not. The antecedent
circumstances are these: A sheep or heifer is attacked with the disease
known in France as _charbon_, in Germany as _milz-brand_, and in England
as _splenic fever_. Its blood on examination would be found plentifully
peopled with bacteria. If a lancet were plunged into the body of the
animal, and were then used to slightly scratch or cut the skin of a man,
he would be inoculated with "charbon." The bite of the fly is precisely
similar in its action. Its rostrum has been smeared with the poisoned
blood, an infinitesimal particle of which is sufficient to inclose
several of the disease "germs," and these are then transferred to the
blood of the next man or animal which the fly happens to bite. The
disease is reproduced as simply and certainly as the spores of some
species of fern give rise to their like if scattered upon soil suitable
for their growth. But flies which do not bite may transfer infection.
Every one must know that if blood be spilt upon the ground a crowd of
flies will settle upon and eagerly absorb it. Animals suffering from
splenic fever in the later stages of the disease sometimes emit bloody
urine. Often they are shot or slaughtered by way of stamping out the
plague, and their carcasses are buried deep in the ground. But some loss
of blood is sure to happen, and this will mostly be left to soak into
the ground. Here again the flies will come, and their feet and mouth
will become charged with the contagion. Such a fly, settling upon
another animal or a man, and selecting--as it will do by preference, if
such exist--a wound, or a place where the skin is broken, will convey
the disease.
Again, M. Pasteur has thoughtfully pointed out that if an animal has
died of splenic fever, and has been carefully buried, the earth-worms
may bring up portions of infectious matter to the surface, so that sheep
grazing, or merely being folded over the spot in question, may take the
plague and die. Hence be wisely counsels that the bodies of such animals
should be buried in sandy or calcareous soils where earth-worms are not
numerous. But it is perfectly legitimate to go a step farther. If such
worm-borings retain the slightest savor of animal matter, flies will
settle upon them and will convey the infectious dust to the most
unexpected places, giving wings to the plague.
Now it is very true that no one has seen a fly feasting upon the blood
of a heifer or sheep dying or just dead of splenic fever, has then
watched it settle upon and bite some person, and has traced the
following stages of the disease. But it is positively known that a
person has been bitten by a fly, and has then exhibited all the symptoms
of charbon, the place of the bite being the primary seat of the
infection. We know also, beyond all doubt, the eagerness with which
flies will suck up blood, and we likewise know the strange persistence
of the disease "germs."
Again, the avidity of flies for purulent matter is not a thing of mere
possibility. In Egypt, where ophthalmia is common, and where the "plague
of flies" seems never to have been removed, it is reported as almost
impossible to keep these insects away from the eyes of the sufferers.
The infection which they thus take up they convey to the eyes of persons
still healthy, and thus the scourge is continually multiplied.
A third case which seems established beyond question is the agency of
mosquitoes in spreading elephantiasis. These so-called sanitary agents
suck from the blood of one person the Filariae, the direct cause of the
disease, and transfer them to another. The manner in which this process
is effected will appear simple enough if we reflect that the mosquito
begins operations by injecting a few drops of fluid into its victim, so
as to dilute the blood and make it easier to be sucked.
So much being established it becomes in the highest degree probable that
every infectious disease may be, and actually is, at times propagated
by the agency of flies. Attention turned to this much neglected quarter
will very probably go far to explain obscure phenomena connected with
the distribution of epidemics and their sudden outbreaks in unexpected
quarters. I have seen it stated that in former outbreaks of pestilence
flies were remarkably numerous, and although mediaeval observations on
Entomology are not to be taken without a grain of salt, the tradition
is suggestive. Perhaps the Diptera have their seasons of unusual
multiplication and emigration. A wave of the common flea appears to have
passed over Maidstone in August, 1880.
We now see the way to some practical conclusions not without importance.
Recognizing a very considerable part of the order of Diptera, or
two-winged flies, as agents in spreading disease, it surely follows
that man should wage war against them in a much more systematic and
consistent manner than at present. The destruction of the common
house-fly by "_papier Moure_," by decoctions of quassia, by various
traps, and by the so-called "catch 'em alive," is tried here and there,
now and then, by some grocer, confectioner, or housewife angry at the
spoliation and defilement caused by these little marauders. But there
is no concerted continuous action--which after all would be neither
difficult nor expensive--and consequently no marked success. Experiments
with a view of finding out new modes of fly-killing are few and far
between.
Every one must occasionally have seen, in autumn, flies as if cemented
to the window-pane, and surrounded with a whitish halo. That in some
seasons numbers of flies thus perish--that the phenomenon is due to a
kind of fungus, the spores of which readily transfer the disease from
one fly to another--we know. But here our knowledge is at fault. We
have not learnt why this fly-epidemic is more rife in some seasons than
others. We are ignorant concerning the methods of multiplying this
fungus at will, and of launching it against our enemies. We cannot tell
whether it is capable of destroying _Stomoxys calcitram_, the blowflies,
gadflies, gnats, mosquitoes, etc. Experiment on these points is rendered
difficult by the circumstance that the fungus is rarely procurable
except in autumn, when some of the species we most need to destroy are
not to be found. Another question is whether the fungus, if largely
multiplied and widely spread, might not prove fatal to other than
Dipterous insects, especially to the Hymenoptera, so many of which,
in their character of plant-fertilizers, are highly useful, or rather
essential to man.
Another fungus, the so-called "green muscardine" (_Isaria destructor_),
has been found so deadly to insects that Prof. Metschnikoff, who is
experimenting upon it, hopes to extirpate the _Phylloxera_, the Colorado
beetle, etc., by its agency.
Coming to better known and still undervalued fly-destroyers, we have
interfered most unwisely with the balance of nature. The substitution of
wire and railings for live fences in so many fields has greatly lessened
the cover both for insectivorous birds and for spiders. The war waged
against the latter in our houses is plainly carried too far. Whatever
may be the case at the Cape, in Australia, or even in Southern Europe,
no British species is venomous enough to cause danger to human beings.
Though cobwebs are not ornamental, save to the eye of the naturalist,
there are parts of our houses where they might be judiciously tolerated:
their scarcity in large towns, even where their prey abounds, is
somewhat remarkable.
But perhaps the most effectual phase of man's war against the flies will
be negative rather than positive, turning not so much on putting to
death the mature individuals as in destroying the matter in which the
larvae are nourished. Or if, from other considerations, we cannot
destroy all organic refuse, we may and should render it unfit for the
multiplication of these vermin. We have, indeed, in most of our large
towns and in their suburbs, abolished cesspools, which are admirable
breeding-places for many kinds of Diptera, and which sometimes presented
one wriggling mass of larvae. We have drained many marshes, ditches,
and unclean pools, rich in decomposing vegetable matter, and have thus
notably checked the propagation of gnats and midges. I know an instance
of a country mansion, situate in one of the best wooded parts of the
home counties, which twenty years ago was almost uninhabitable, owing to
the swarms of gnats which penetrated into every room. But the present
proprietor, being the reverse of pachydermatous, has substituted covered
drains for stagnant ditches, filled up a number of slimy ponds as
neither useful nor ornamental, and now in most seasons the gnats no
longer occasion any annoyance.
But if we have to some extent done away with cesspools and ditches, and
have reaped very distinct benefit by so doing, there is still a grievous
amount of organic matter allowed to putrefy in the very heart of our
cities. The dust bins--a necessary accompaniment of the water-carriage
system of disposing of sewage--are theoretically supposed to be
receptacles mainly for organic refuse, such as coal-ashes, broken
crockery, and at worst the sweepings from the floors. In sober fact
they are largely mixed with the rinds, shells, etc., of fruits and
vegetables, the bones and heads of fish, egg-shells, the sweepings out
of dog-kennels and henhouses, forming thus, in short, a mixture of evil
odor, and well adapted for the breeding-place of not a few Diptera.
The uses to which this "dust" is put when ultimately fetched away are
surprising: without being freed from its organic refuse it is used to
fill up hollows in building-ground, and even for the repair of roads. A
few weeks ago I passed along a road which was being treated according
to the iniquity of Macadam. Over the broken stones had been shot, to
consolidate them, a complex of ashes, cabbage-leaves, egg and periwinkle
shells, straw, potato-parings, a dead kitten (over which a few
carrion-flies were hovering), and other promiscuous nuisances. The road
in question, be it remarked, is highly "respectable," if not actually
fashionable. The houses facing upon it are severely rated, and are
inhabited chiefly by "carriage people." What, then, may not be expected
in lower districts?
Much attention has lately been drawn to the fish trade of London. It has
_not_, however, come out in evidence that the fish retailers, if they
find a quantity of their perishable wares entering into decomposition,
send out late in the evening a messenger, who, watching his opportunity,
throws his burden down in some plot of building land, or over a fence.
When I say that I have seen in one place, close alongside a public
thoroughfare, a heap of about fifty herrings, in most active
putrefaction and buzzing with flies, and some days afterward, in another
place, some twenty soles, it will be understood that such nuisances
can only be occasioned by dealers. To get rid of, or at least greatly
diminish, carrion-flies, house-flies, and the whole class of winged
travelers in disease, it will be, before all things, essential to
abolish such loathsome malpractices. The dustbins must cease being made
the receptacle for putrescent and putrescible matter, the destruction of
which by fire should be insisted upon.
The banishment of slaughter-houses to some truly rural situation, where
the blood and offal could be at once utilized, would be another step
toward depriving flies of their pabulum in the larva state. An equally
important movement would be the substitution of steam or electricity for
horsepower in propelling tram-cars and other passenger carriages, with a
view to minimize the number of horses kept within greater London. Every
large stable is a focus of flies--_Journal of Science_.
* * * * *
ON THE RELATIONS OF MINUTE ORGANISMS TO CERTAIN SPECIFIC DISEASES.
At the recent Medical Congress in London, Professor Klebs undertook to
answer the question: "Are there specific organized causes of disease?"
A short historical review of the various opinions of mankind as to the
origin of disease led, the speaker thought, to the presumption that
these causes were specific and organized.
If we now, he said, consider the present state of this question, the
three following points of view present themselves as those from which
the subject may be regarded:
I.--We have to inquire whether the lower organisms, which are found in
the diseased body, may arise there spontaneously; or whether even they
may be regarded as regular constituents of the body.
II.--The morphological relations of these organisms have to be
investigated, and their specific nature in the different morbid
processes has to be determined.
III.--We have to inquire into their biological relations, their
development inside and outside the body, and the conditions under which
they are able to penetrate into the body, and there to set up disease.
_First_.--With regard to the first question, that of the possibility of
spontaneous generation, the speaker gave a decided negative.
_Second and third_.--There is in microscopic organisms a difference of
form corresponding, as a rule, to difference of function. The facts
regarding these various lower forms are briefly reviewed.
"Three groups of hyphomycetae, algae, and schizomycetae, have been
demonstrated to occur in the animal and human organism in infective
diseases. Their significance increases with the increase of their
capacity for development in the animal body. This depends partly upon
their natural or ordinary conditions of life, but partly also, and that
in a very high degree, upon their power of adaptation, which, as Darwin
has shown, is a property of all living things, and causes the production
of new species with new active functions.
"1. The hyphomycetae, on account of their needing an abundant supply
of oxygen, give rise to but few morbid processes, and these run their
course on the surface of the body, and are hence relatively of less
importance. It will be sufficient here to refer to the forms, achorion,
trichophyton, oidium, aspergillus, and the diseases produced by them,
favus, ringworm, and thrush, to show this peculiarity. Nevertheless, we
see that these organisms also (as was proved by the older observations
of Hannover and Zenker) may, under certain circumstances, penetrate into
the interior of the organs. Grawitz, moreover, has recently shown that
their faculty of penetrating into the interior of the organism, and
there undergoing further development, depends on their becoming
accustomed to nitrogenous food.
"2. Only one of the algae, viz., leptothrix, has as yet acquired any
importance as a producer of disease. It gives rise to the formation of
concretions, and that not only in the mouth, but also, as I have shown,
in the salivary ducts and urinary bladder.
"Another alga, the sarcina of Goodsir, may indeed pass through the
organism, without, however, producing in its passage either direct
or indirect disturbances. It seems more worthy of note that many
schizomycetae, and especially the group of bacilli, are evidently nearly
allied to the algae in their morphological and vegetative relations--so
as to be assigned to this class by several authors, and especially by
Cienkowski.
"The schizomycetae furnish, without doubt, by far the most numerous
group of infective diseases. We distinguish within this group two
widely different series of forms, which we will speak of as bacilli and
cocco-bacteria respectively. The former, which was first exhaustively
described by Ferdinand Cohn, and the pathological importance of which,
especially in relation to the splenic disease of cattle, was first shown
by Koch, consist of threads, in the interior of which permanent or
resting-spores are developed. These spores becoming free, are able,
under suitable conditions of life, again to develop into threads. The
whole development of these organisms, and especially the formation
of spores, is completed on the surface of the fluids, and under the
influence of an abundant supply of oxygen.
"The number of affections in which these organisms have been found,
and which may be to a certain extent produced artificially by the
introduction of these organisms into healthy animal bodies, has been
largely increased since the discovery of Koch, that the bacteria of
splenic fever (anthrax) belong to this group. Under this head must be
placed the bacillus malarise (Klebs and Tommassi-Crudeli), the bacillus
typhi abdominalis (Klebs, Ebert), the bacillus typhi exanthematici
(Klebs, observations not yet published), the bacillus of hog-cholera
(Klein), and, finally the bacillus leprosus (Neisser). It would exceed
the time appointed were I to attempt to describe these forms more
minutely. This may, perhaps, be better reserved for discussion and
demonstration.
"Alongside of these general infective diseases produced by bacilli,
local affections also occur, which indicate the presence of these
organisms at the point where disease begins. As an example of these
processes, which probably occur in various organs, I would mention
gastritis bacillaris, of which I shall show you preparations. In this,
we can trace the entrance of the bacilli into the peptic glands, as well
as their further distribution in the walls of the stomach, and in the
vascular system.
"The second group of the pathogenetic schizomycetae I propose to call,
with Billroth, cocco-bacteria, because they consist of collections of
micrococci, which are capable of transforming themselves into short
rods. The former usually form groups united by zooegloea; by prolongation
of the cocci rods are formed, which sprout out, break up by division
into chains, and further lead again to the formation of resting masses
of cocci. I distinguish, further, in this group, two genera--the
microsporina and the monadina; in the former of which the micrococci are
collected into spherical lumps, in the latter into layers. The one class
is developed in artificial cultivation fluid, the other on the surface.
The former requires a medium poor in oxygen, the latter a medium rich in
oxygen, for their development.
"Among the affections produced by microsporina, I reckon especially the
septic processes, and also true diphtheria. On the other hand, to the
processes produced by monadina belong especially a large series of
diseases, which according to their clinical and anatomical features,
may be characterized as inflammatory processes, acute exanthemata, and
infective tumors, or leucocytoses. Of inflammatory processes, those
belong here which do not generally lead to suppuration, such as
rheumatic affections, including the heart, kidney, and liver affections,
which accompany this process, sequelae which, as is well known,
lead more especially to formation of connective tissue, and not to
suppuration. Here, also, belong croupous pneumonia, the allied disease
erysipelas, certain puerperal processes, and finally, parotitis
epidemica, or mumps.
"Among the acute exanthemata, the following may, up to the present time,
be placed in this group; variola-vaccina, scarlatina, and measles.
"The group of infective tumors is represented by tuberculosis, syphilis,
and glanders. Throughout the whole group of cocco-bacteria the
demonstration of organisms in the diseased parts encounters difficulties
which vary considerably in the different kinds."
The speaker concluded by describing the methods (now well known) by
which the powers of the different organisms are tested.
He also referred to Pasteur's, Chauveau's, and Toussaint's recent
experiments.
His conclusion was that the specific communicable diseases are produced
by specific organisms.
* * * * *
THE CENTENARY OF THE DISCOVERY OF URANUS.
By W. F. DENNING, F.R.A.S.
The year 1781 was signalized by an astronomical discovery of great
importance, and one which marked the epoch as memorable in the annals
of science. A musician at Bath, William Herschel by name, who had been
constructing some excellent telescopes and making a systematic survey of
the heavens, observed an object on the night of March 13 of that year,
which ultimately proved to be a large planet revolving in an orbit
exterior to that of Saturn. The discovery was as unique as it was
significant. Only five planets, in addition to the Earth, had hitherto
been known; they were observed by the ancients, and by each succeeding
generation, but now a new light burst upon men. The genius of Herschel
had singled out from the host of stars which his telescope revealed
an object the true character of which had evaded human perception for
thousands of years!
[Illustration: FIG. 1.--APPROXIMATE PLACE OF URANUS AMONGST THE STARS AT
ITS DISCOVERY ON MARCH 13, 1781]
The centenary of this remarkable advance in knowledge naturally recalls
to mind the circumstances of the discovery, and makes us inquisitive to
know what new facts have been gleaned of Herschel's planet, now that
a hundred years have passed away, and we are enabled to look back and
review the vast amount of labor which has been accomplished in this wide
and attractive field of astronomical research. We may learn what new
features have been discerned of the new body, and what additional
discoveries in connection with other planets unknown in Herschel's day,
have been effected by aid of the powerful telescopes which have been
devoted to the work. We do not, however, intend dealing with the general
question of planetary discovery, for at a glance we are impressed with
its magnitude. While a century ago five planets only were known, we now
have some two hundred and thirty of these bodies, and the stream of
discovery flows on without abatement through each succeeding year. The
detection of Uranus seems, indeed, to have been the prelude to many
similar discoveries, and to have offered the incentive to greater
diligence and energy on the part of observers in various parts of the
world.
[Illustration: Fig. 2.--ORBITS OF THE URANIAN SATELLITES.]
Many great discoveries have resulted from accident; and the leading
facts attending that of Uranus prove that, in a large measure, the
result was brought about in a similar way. Herschel, as he unwearyingly
swept the heavens night after night, was in quest of sidereal
wonders--such as double stars and nebulae--and he happened to alight
upon the new planet in a purely chance way. He had no expectation of
finding such a remarkable object, and indeed, when he had found it,
wholly mistook its character. There could be no doubt that it was a body
wholly dissimilar to the fixed stars, and it was equally certain that it
could not be a nebula. It had a perceptible disk, for when it had first
come under the critical eye of its discoverer he had noticed immediately
that its appearance differed widely from the multitude of objects which
crossed the field of his telescope. He had been accustomed to see hosts
of stars pass in review, and their aspect was in one respect similar,
namely, they were invariably presented as points of light incapable of
being sensibly magnified, even with the highest powers. True, there was
a great variety of apparent brightness in these objects and a singular
diversity of configuration, but there was no exception to the invariable
feature referred to. The point of light was constant, and no striking
exception was anticipated until one night--March 13, 1781--Herschel
being intently engaged in the examination of some small stars in the
region of Gemini, brought an object under the range of, his telescope,
which his eye at once selected as one of anomalous character.
Applying a higher power, he noticed that it exhibited a planetary disk,
but his instrument failed to define it with sufficient distinctness, and
hence he became doubtful as to its real nature. The object was found to
be in motion, and subsequent observations led him to the assumption that
it must be a comet of rather exceptional type. This appeared to be the
best explanation of the strange body, for history contained many records
of curious comets, some of which were observed as nearly circular
patches of nebulous light, and probably of similar aspect to the object
then visible; and apart from this it must be remembered that the idea of
a large planet exterior to Saturn was a fact of such momentous import
that Herschel, with a due regard to that modesty which accompanies
true genius, refrained from attaching such an interpretation to his
observations. He was content to direct the notice of astronomers to it
as a phenomenon requiring close attention, and suggested that it might
be a comet in consequence of its motion and the faint and somewhat
ill-defined character of its appearance.
From the earliest ages five planets only were known, and the discovery
of another large planet beyond the sphere of Saturn must at once
revolutionize existing ideas as to the range of the solar system, and
immediately take rank as a scientific event of equal interest to the
discovery of the moons of Jupiter or the rings of Saturn, which each in
their day impressed men with new ideas of the celestial mechanism. But
the truth could not long be delayed. The new body being watched and its
orbit rigorously computed from a series of observed positions revealed
its true character, and Herschel was awarded the honor due to the author
of a discovery of such importance. His diligence and pertinacity alone
had enabled him to search out from among the multitude of stars thickly
strewn over the firmament this unknown and well-nigh invisible planet
which, during all the preceding years of the world's history, had eluded
human perception. Men had been all unconscious of its existence as it
had been slowly completing its circuits around the sun, obedient to the
same laws as the other planets of the solar system, and awaiting the
hour when the unfailing eve of Herschel should introduce it as the faint
and far-off planet girding our system within its expansive folds.
As soon as the existence of the new orb was confirmed and the fact
rendered indisputable, the question naturally arose whether it had ever
been seen in former years by the authors of star catalogues, who could
hardly have overlooked an object like this though its planetary nature
had manifestly escaped detection. It was just perceptible to the naked
eye, shining like a star of the sixth magnitude, and ought to have been
distinguished by those who had reviewed the heavens with the purpose
of determining and mapping the positions of the stars. Reference was,
therefore, made to the chief catalogues, when it was found at once that
the planet had been unquestionably observed by Tobias Mayer, Le Monnier,
Bradley, and Flamsteed. It was several times noted by these observers:
by Le Monnier no less than twelve times, and by Flamsteed on six
occasions; and it is remarkable that in every instance its true
character escaped detection. Neither its special appearance nor its
motion attracted attention, so that it was merely catalogued as an
ordinary fixed star. Thus Herschel was not anticipated in his discovery.
It remained for him, in 1781, to note its exceptional aspect, and to
specify it as an object requiring critical investigation. But the early
observations above alluded to served a useful purpose in testing the
accuracy of the computed orbit, for without waiting many years to
compare the theoretical and observed positions, astronomers had in these
old records a reliable series of points through which the previous
course of the planet could be traced.
The calculations showed that its mean distance from the sun was some
1,750,000,000 miles, and that a revolution was completed in about
eighty-four years. It was also found to be a very large planet, greatly
exceeding either Mercury, Venus, the Earth, or Mars, though considerably
inferior to either Jupiter or Saturn.
Here, then, was a discovery of the utmost importance, and one of the
most salient additions to our knowledge which the telescope had ever
achieved. The new planet was now definitely assigned its proper place in
the solar system, and was regarded as of equal significance with the
old planets. True, the new planet of Herschel could not be compared as
regards its visible aspect with the other previously known members of
our system, but it was nevertheless an object of equal weight. Its vast
distance alone rendered it faint. It formed one of the constituent parts
of the solar system, which, though separated by immense intervals of
space, are yet coherent by the far-reaching effects of gravitation.
There is, indeed, a bond of harmony between the series of planetary
orbits, which exhibit a marked degree of regularity in their successive
distances from the sun; and though they are not connected by any visible
links, they are firmly held together by unseen influences, and their
motions are subject to certain laws which have been revealed by
centuries of observation.
The question of suitably naming the new planet soon came to the fore.
Herschel himself proposed to designate it the "Georgium Sidus," in honor
of his patron, George III., just as Galileo had called the satellites
of Jupiter the "Medicean stars," after Cosmo de' Medici. But La Place
proposed that the planet should be named after its discoverer; and thus
it was frequently referred to as "Herschel," and sometimes as "The
Herschelian planet." Astronomers on the continent objected to this
system of personal nomenclature, and argued that the new body should
receive an appellative in accordance with those adopted for the old
planets, which had been selected from the heathen mythology. Several
names were suggested as suitable (on the basis of this principle), and
ultimately the one advanced by Bode received the most favor, and the
planet thereafter was called "Uranus."
The varying positions of the new body as observed on successive nights
were determined by comparisons with a group of six small stars, termed
by Herschel [Greek: alpha, beta, gamma, delta, epsilon] and afterwards
formed into a constellation under the designation of "Britannia," though
it does not appear that this little asterism is acknowledged as one of
our constellations. Its position is about midway between Taurus and
Gemini, and the following are the principal stars computed for 1881.0,
as given by Mr. Marth:
Star. Magnitude. Right Ascension. Declination.
h. m. s.
alpha 9.0 5 42 6.06 23 deg. 35' 6.7" N.
eta 8.7 5 43 17.82 23 26' 7.2 N.
theta 8.8 5 44 0.99 23 53' 30.8 N.
epsilon 8.8 5 45 40.68 23 34' 46.8 N.
The stars are therefore merely telescopic, and are confined to a small
area of space, so that the propriety of adopting the group as a distinct
constellation is very questionable. Their positions close to Uranus at
the time of its discovery, and the fact that the planet's motion was
detected by means of comparisons with them, has given to these stars an
historical interest which in future years must often attract the student
to their reobservation. But it would be unwise, as forming a bad
precedent, to accept a group of stars of this inferior type as meriting
to rank among the old constellations, when we have numbers of richer
groups, situated on their confines, which first deserve such a
distinction. However special or unique the circumstances connected with
certain telescopic stars may be, and however necessary it may appear
to signalize them by a specific title, we are inclined to question the
adoption of such means as likely to exercise a wrong influence,
inasmuch as it may hereafter originate further innovations of a similar
character, and ultimate complications will be certain to arise.
Soon after the discovery of Uranus it was suspected that the planet
was encircled, like Saturn, by a luminous ring, but on subsequent
observation this was not confirmed, and no such appendage has ever been
revealed in the more perfected instruments of our own times. Indeed, if
Uranus displays a peculiarity of constitution in any way analogous to
the ring system of Saturn, it must be of the most minute character so as
to have thus evaded telescopic scrutiny during a hundred years.
The discovery soon attracted the notice of royalty, and the reigning
sovereign, George III., anxious to practically express his appreciation
of the valuable labors of Herschel, awarded him a pension of L200 a year
and furnished him with a residence at Slough, near Windsor, and the
means to erect a gigantic telescope with which he might be enabled
to continue his important researches. This instrument consisted of a
reflector on the "Front-view" construction, with a speculum 4 feet in
diameter and of 40 feet focal length. Upon its completion, Herschel
immediately began to observe the region of the new planet with the idea
of discovering any satellites which might belong to it, for analogy
suggested that it was surrounded by a numerous retinue of such bodies.
He was soon successful, for, on the night of January 11, 1787. he saw
two minute objects near the planet, which renewed observations revealed
to be satellites; and he detected two additional ones in 1790, and two
others in 1794, making six in all. But the observations were of extreme
difficulty. The path of the planet frequently passed near minute stars,
and it became hard to distinguish between them and the suspected
satellites. Herschel, however, considered he had obtained conclusive
evidence of the existence of six satellites with sidereal periods
ranging from 5d. 21h. 25m. to 107d. 16h. 39m., and his means of
observation being much superior to those possessed by any of his
contemporaries it was impossible to have corroborative testimony.
The matter was thus allowed to rest until the middle of the present
century, when Lassell, in the pure sky at Malta, endeavored to reobserve
the satellites with a two-foot reflector. This instrument was considered
superior to Herschel's telescope; and the atmosphere at this station
being decidedly more suitable for such delicate observations than
in England, it was removed there for the express purpose of dealing
successfully with objects of extreme difficulty. The results were very
important. Mr. Lassell became convinced that Uranus had only four
satellites, and that if any others existed they remained to be
discovered. Two of these were found to be identical with those seen by
Herschel in 1787, and now called Titania and Oberon. The other two,
Ariel and Umbriel, could not be identified with any of those alleged to
have been previously detected by Herschel, so that the inference was
that they were new bodies, and that the priority of discovery was due to
Mr. Lassell; whence it also followed that the older observations were
erroneous, and that in fact Herschel had been entirely mistaken with
regard to the four satellites he believed he had detected subsequently
to 1787.
In November, 1873, a fine twenty-six-inch object glass, by Alvan Clark,
was mounted at the U. S. Naval Observatory at Washington, and it was
soon employed upon the difficult task of solving the problem as to the
exact periods of the Uranian satellites. This was very satisfactorily
effected, and with distinct and conclusive favor to Mr. Lassell, whose
observations were fully corroborated. Only four satellites could be
distinguished by the American observers, and their periods, as computed
from a valuable series of measures, agreed with those previously derived
at Malta. In Appendix I. to the "Washington Observations" for 1873,
Prof. Newcomb gave a valuable summary of results--the first obtained, be
it noted, with that splendid instrument which soon afterward, in 1877,
revealed the satellites of Mars--which included the elements of the
satellites of Uranus as follows:
Mean Longitude.
Satellite. Epoch 1871. Radius of Period of
Dec. 31, W.M.T. Orbit. Revolution in days.
I. Ariel........ 21.83 deg. 13.78" 2.52038
II. Umbriel..... 13.52 19.20 4.14418
III. Titania..... 229.93 31.48 7.70590
IV. Oberon...... 154.83 42.10 13.43327
Speaking of the comparative brightness of the satellites, Prof. Newcomb
says:
"The greater proximity of the inner satellites to the planet makes it
difficult to compare them photometrically with the outer ones, as actual
feebleness of light cannot be distinguished from difficulty of seeing
arising from the proximity of the planet. However, that Umbriel is
intrinsically fainter than Titania is evinced by the fact that, although
the least distance of the latter is somewhat less than the greatest
distance of the former, there is never any difficulty in seeing it in
that position. From their relative aspects in these respective positions
I judge Umbriel to be about half as bright as Titania. Ariel must be
brighter than Umbriel, because I have never seen the latter unless it
was farther from the planet than the former at its maximum distance....
I think I may say with considerable certainty that there is no satellite
within 2' of the planet, and outside of Oberon, having one-third the
brilliancy of the latter, and therefore that none of Sir William
Herschel's supposed outer satellites can have any real existence. The
distances of the four known satellites increase in so regular a way that
it can hardly be supposed that any others exist between them. Of what
may be inside of Ariel it is impossible to speak with certainty, since
in the state of atmosphere which prevails during our winter all the
satellites named disappear at 10" from the planet."
Prof. Newcomb mentions that no systematic search for new satellites
was undertaken because it must have interfered with the fullness and
accuracy of the micrometer measures of the old satellites, which
constituted the main purpose of the observations. Some faint objects
were occasionally glimpsed near the planet, and their relative places
determined, but they were never found to accompany Uranus. The fact,
therefore, that no additional satellites were discovered is not to
be regarded as a strong point in favor of the theory of their
non-existence, because the great power and excellence of the telescope
was expressly directed to the attainment of other ends; and moreover the
season in which the planet came to opposition was distinctly unfavorable
for the prosecution of a rigorous search for new satellites. There
can, however, be no doubt that the analogies of the planetary systems
interior to Uranus plainly suggest that this planet is attended by
several satellites which the power of our greatest telescopes has
hitherto failed to reveal; and that it is in this direction and that of
Neptune we may anticipate further discoveries in future years when the
conditions are more auspicious and the work is entered upon with special
energy, aided by instruments of even greater capacity than those which
have already so far conduced to our knowledge of the heavenly bodies.
Notwithstanding the extreme difficulty with which the Uranian satellites
are observed, the two brighter ones, Titania and Oberon, discovered by
William Herschel in 1787, have been occasionally detected in telescopes
of moderate power, and identified by means of an ephemeris which has
shown that the computed positions approximately agree with those
observed. During the last few years Mr. Marth has published ephemerides
of the satellites of both Saturn and Uranus, and many amateurs have to
acknowledge the valuable aid rendered by these tables, which supply a
ready means of identifying the satellites, and thus act as an incentive
to observers who are induced to pursue such work for the sake of the
interesting comparisons to be made afterward. In one exceptional
instance the two outer satellites of Uranus appear to have been glimpsed
with an object glass of only 43 inches aperture, and the facts are given
in detail in the "Monthly Notices of the R.A.S.," April 1876, pp. 294-6.
The observations were made in January, February, and March, 1876, by
Mr. J.W. Ward, of Belfast; and the positions of the satellites, as he
estimated them on several nights, are compared with those computed, the
two sets presenting tolerably good agreement. Indeed the corroborations
are such as to almost wholly negative any skepticism, though such
extraordinary feats should always be received with caution.
In this particular case the chances of being misled are manifold; even
Herschel himself fell into error in taking minute stars to be satellites
and actually calculating their periods; so that when we remember the
difficulties of the question our doubts are not altogether dispelled.
Extreme acuteness of vision will, in individual instances, lead to
success of abnormal character, and certainly in Mr. Ward's case the
remarkable accordances in the observed and calculated positions appear
to be conclusive evidence that he was not mistaken.
It will be readily inferred that the great distance and consequent
feebleness of Uranus must render any markings upon the disk of the
planet beyond the reach of our best telescopes; and indeed this appears
to have been a matter of common experience. Though the surface has been
often scanned for traces of spots, we seldom find mention that any have
been distinguished. Consequently the period of rotation has yet to be
determined. It is true that an approximate value was assigned by Mr.
T.H. Buffham from observations with a nine-inch reflector in 1870 and
1872. but the materials on which the computation was based were slender
and necessarily somewhat uncertain, so that his period of about twelve
hours stands greatly in need of confirmation. The bright spots and zones
seen on the disk in the years mentioned appear to have entirely eluded
other observers, though they are probably phenomena of permanent
character and within reach of instruments of moderate size. Mr. Buffham
[1] thus describes them:
[Footnote 1: "Monthly Notices K. A. S.," January, 1873.]
"1870, Jan. 25, 11h. to 12h. in clear and tolerably steady air; power
132 showed that the disk was not uniform. With powers 202 and 3.0, two
round, bright spots were perceived, not quite crossing the center but a
little nearer to the eastern side of the planet, the position angle of a
line passing through their centers being about 20 and 200--ellipticity
of Uranus seemed obvious, the major axis lying parallel to the line of
the spots.
"Jan. 27, 10h. to 101/2h.; some fog, and definition not good, but the
appearance of the spots was almost exactly the same as on the 25th."
On March 19 glimpses were obtained of a light streak and two spots.
On April 1, 4, 6, and 8, a luminous zone was seen on the disk, and
in February and March, 1872, when observations were resumed, certain
regions were noted brighter than others, and underwent changes
indicating the rotation of the planet in a similar direction to that
derived from the results obtained in 1870. Mr. Buffham points out that,
if this is admitted, then the plane of the planet's equator is not
coincident with the plane of the orbits of the satellites. Nor need we
be surprised at this departure from the general rule, where such an
anomalous inclination exists. In singular confirmation of this is Mr.
Lassell's observation of 1862, Jan. 29, where he says: "I received an
impression which I am unable to render certain of an equatorial dark
belt, and of an ellipticity of form."
Some observations made in 1872-3 with the great six-foot reflector of
Lord Rosse may here be briefly referred to. A number of measures, both
of position and distance, of Oberon and Titania, were made, [1] and a
few of Umbriel and Ariel, but "the shortness of the time available (40
minutes) each night for the observation of the planet with the six-foot
instrument, the atmospheric disturbance, so often a source of annoyance
in using so large an aperture, and other unfavorable circumstances,
tended to affect the value of the observations, and to make the two
inner satellites rarely within detection."
[Footnote 1: "Monthly Notices R. A. S.," March, 1875.]
On Feb. 10, 1872, Lord Rosse notes that all four satellites were seen on
the same side of the planet. On Jan. 16, 1873, when definition was good,
no traces of any markings were seen. Diameter of Uranus = 5.29". Power
414 was usually employed, though at times the inner satellites could be
more satisfactorily seen with 625.
It may be mentioned as an interesting point that, some fifty years
after the first discovery of Uranus by Herschel, it was accidentally
rediscovered by his son, Sir John Herschel, who recognized it by
its disk, and had no idea as to the identity of the object until an
ephemeris was referred to. Sir John mentions the fact as follows, in a
letter to Admiral Smyth, written in 1830, August 8:
"I have just completed two twenty-foot reflectors, and have got some
interesting observations of the satellites of Uranus. The first sweep
I made with my new mirror I _re-discovered_ this planet by its _disk_,
having blundered upon it by the merest accident for 19 Capricorni."
In commenting upon the centenary of an important scientific discovery we
are naturally attracted to inquire what progress has been made in the
same field during the comparatively short interval of one hundred years
which has elapsed since it occurred. We have called it a short interval,
because it cannot be considered otherwise from an astronomical or
geological point of view, though, as far as human life is concerned,
it can only be regarded as a very lengthy period, including several
generations within its limits.
Since Herschel, in 1781, discovered Uranus, astronomy has progressed
with great rapidity, so that it would be impossible to enumerate in a
brief memoir the many additional discoveries which have resulted from
assiduous observation. A century ago only five planets were known
(excluding the Earth), now we are acquainted with about two hundred and
thirty of these bodies; and one of these, found in 1846, is a large
planet whose orbit lies exterior to that of Uranus. In fact, the state
of astronomical knowledge a century ago has undergone wonderful changes.
It has been rendered far more complete and comprehensive by the
diligence of its adherents and by the unwearying energy with which both
in theory and practice it has been pursued. A zone of small planets has
been discovered between Mars and Jupiter just where the analogies of the
planetary distances indicated the probable existence of a large planet.
The far-off Neptune was revealed in 1846 by a process of analytical
reasoning as unique as it was triumphant, and which proved how well
the theory of planetary perturbations was understood. The planet was
discovered by calculation, its position in the heavens assigned, and the
telescope was then employed merely as the instrument of its detection.
The number of satellites which a century ago numbered only ten has now
reached twenty, and the discovery in 1877 of two moons accompanying Mars
shows that the work is being continued with marked success.
In other departments we also find similar evidence of increasing
knowledge. The periodicity of the sun spots, the existence of systems of
binary stars, meteor showers, and their affinity with cometary orbits
may be mentioned as among the more important, while a host of new
comets, chiefly telescopic, have been detected. Large numbers of nebulae
and double stars have been catalogued, and we have evidence every year
of the activity with which these several branches are being followed up.
In fine, it matters little to what particular department of astronomical
investigation we look for traces of advancement during the past hundred
years, for it is evident throughout them all, and sufficiently proves
that the interest formerly taken in the science has not only been well
sustained but has become more general and popular, and is extending its
attractive features to all classes of the community.
In Herschel's day large telescopes were rare. A man devoting himself to
the study of the heavenly bodies as a means of intellectual recreation
was considered a phenomenon, and indeed that appellation might be
fittingly applied to the few isolated individuals who really occupied
themselves in such work. How different is the case now that the pleasant
ways of science have called so many to her side and so far perfected her
means of research as to make them accessible to all who care to see and
investigate for themselves the unique and wonderful truths so easily
within reach! Large telescopes have become common enough, and there is
no lack of hands and eyes to utilize them, nor of understanding, ever
ready to appreciate, in sincerity and humbleness, those objects which
display in an eminent degree the all-wise conceptions of a great
Creator! It is, therefore, a most gratifying sign to notice this rapid
development of astronomy, and to see year by year the increasing number
of its advocates and the record of many new facts gleaned by vigorous
observation.
The character of recent discoveries distinctly intimates that, in future
years, some departments of the science will become very complicated,
owing to the necessity of dealing with a large number of minute bodies,
for the tendency of modern researches has been to reveal objects which
by their faintness had hitherto eluded detection. And when we consider
that these bodies are rapidly increasing year by year, the idea is
obviously suggested that, inasmuch as their numbers are comparatively
illimitable, and there is likely to be no immediate abatement in the
enthusiasm of observers, difficulties will arise in identifying them
apart and forming them into catalogues with their orbital elements
attached, so that the individual members may be redetected at any time.
In this connection we allude particularly to minor planets, to
telescopic comets, and to meteoric streams, which severally form a very
numerous group of bodies of which the known members are accumulating to
a great extent. As complications arise, some remedies must be applied to
their solution, and one probable effect will be that astronomers will be
induced each one to have a specialty or branch to which his energies are
mainly directed. The science will become so wide in its application and
so intricate in its details that it will become more than ever necessary
for observers to select or single out definite lines of investigation
and pursue them closely, for success is far more likely to attend such
exertions than those which are not devoted to any special end, but
employed rather in a general survey of phenomena.
We have already before us some excellent instances in which individual
energies have been aptly utilized in the prosecution of original work
in some specific branch of astronomy, and we are strongly disposed to
recommend such exclusive labors to those who have the means and the
desire to achieve something useful. Observers who find one subject
monotonous and then take up another for the sake of variation are not
likely to get far advanced in either. In the case of amateurs who use a
telescope merely for amusement, and indiscriminately apply it to nearly
every conspicuous object in the firmament without any particular purpose
other than to satisfy their curiosity, the matter is somewhat different,
and our remarks are not applicable to them. We refer more pointedly
to those who have a regard for the interests of the science and whose
enthusiasm enables them to work habitually and with some pertinacity.
History tells us that the Great Alexander wept when he found he had no
other worlds to conquer, and we fear that some astronomers will lament
that they have little prospect of discovering anything fresh in a sphere
to which our giant telescopes have been so often directed, but this is
founded on a palpable misconception. Certain objects, such as comets for
example, do not require great power, and the revelation of new meteor
showers is entirely a question for the naked eye. In fact, it may be
confidently asserted that observations undertaken with energy and
persistency will, if rightly directed, more than compensate for defects
of instrumental power.
It is true, however, that in certain quarters we must look to large
instruments alone for new discoveries. It would be useless searching for
an ultra-Neptunian planet, or for additional satellites to Uranus or
Neptune, or for the materials to determine the rotation periods of these
planets with a small telescope. Every observer will find objects suited
to the capacity of his instrument, and he may not only employ it
usefully but possibly make a discovery of nearly equal import with that
which rendered the name of Herschel famous a century ago.--_Popular
Science Review_.
* * * * *
THE VARYING SUSCEPTIBILITY OF PLANTS AND ANIMALS TO POISONS AND
DISEASES.
Much attention is being devoted to the causes which determine the
aptitude or immunity with animals for maladies. This is in a general
sense called medical geography, as a physician who has prescribed for
patients in various parts of the world, and belonging to different
races--the white, yellow, and black--has been able to note the
diversities in the same disease, and the contradictions in the remedies
employed.
The true social peril, hardly discovered before we became aware how
to conjure it, lies in those legions of animalcules or microbes that
surround us and in the middle of which we live. M. Pasteur has revealed
them to us as the factors in infectious diseases. Claude Bernard
has demonstrated the community which exists between animals and
vegetables--phenomena of movement, of sensibility, of production of
heat, of respiration, of digestion even, for there are the _Drosera_ and
kindred carnivorous plants. Iron cures chlorosis in vegetables as well
as in animals, and chloroform and ether render both insensible. There
resemblances are more striking still between animals. After Baudrimont,
insects are, in presence of alcohols, chloroform, and irrespirable
gases, similarly affected as man. Many maladies, too, are common to
man and several species of animals; and this organic identity is best
illustrated in the relationship between epidemics and epizootias,
cancer, asthma, phthisis, smallpox, rabies, glanders, charbon, etc.,
afflict alike man and many species of animals.
The differences between races are not less remarkable--odor and taste,
for example. According to anthropophagy, negroes are best, and white
people most detestable. Broca remarked, that, in the dissecting room,
the muscles of the negro putrefied less rapidly than those of whites. It
is perhaps to these anatomical differences that the diverse action of
the same poison, in the case of races or species, may be attributed. On
certain rodentia belladonna exercises no influence; morphine for a horse
is a violent stimulant; a snail remains insensible to digitalis; goats
eat tobacco with impunity; and in the Tarentin the inhabitants rear only
black sheep, because a plant abounds which is noxious for white sheep.
The nature of these conditions is a mystery for science. The _Solanae_
tribe of plants furnish a principle which, as its name implies, produces
consolation or forgetfulness, by acting on the tissues of the brain
where resides the organ of thought; now, on the authority of Professor
Bouchardat, these opiates have the less of effect in proportion as the
animals possess the less of intelligence.
To the same anatomical peculiarities must be ascribed the choice that
disease makes in such or such a race. Glanders, for instance, so
virulent with the horse, the ass, and man, produce in the case of the
dog only a local accident; peripneumonia, so contagious among horned
cattle, is more benign in its action on Dutch than other breeds of
stock; the cattle plague that decimates so many farms is communicated by
cattle to each other from the slightest contact, while the closest and
most constant association is necessary to communicate the disease
to sheep, and even when they are affected its action is not severe.
Further, that plague only attacks ruminant animals--oxen, goats, sheep,
zebras, gazelles, etc. Ten years ago this plague broke out in the Jardin
d'Acclimatation; not a ruminant escaped, and also one animal not of that
class, a little tenant nearly related to the pig--the _peccari_.
Now, Dr. Condereau has demonstrated recently that the stomach of the pig
has a rudimentary organization recalling that of the ruminants. Clearly,
the stomach of the peccari, and perhaps that of the pig, present a
favorable medium for the parasitical microbe peculiar to the rinderpest.
In the potato disease, again, all the varieties are not affected with
the same degree of violence; it is more marked in its action on the
round yellows than the reds, and on the latter rather than the pink. But
the symptoms even of the same malady differ, the parasite's attacks on
the tissues being dissimilar. Oak galls are produced from the prickings
of insects; now around the same larva often four varieties of galls are
recognized. In the case of consumption in cattle, the disease marches
slowly; in that of pigs it takes the galloping form, as with man.
Each people or nation has its peculiar pathology and also its peculiar
cures. A negro can take a dose of tartar ten times more excessive than a
white; the same dose of brandy given to a black, a yellow, and a white,
Back to Full Books
|