8 4 
SCIENCE. 
TRANSLATIONS. 
M. Stroh presented to the Society des Ingdnieurs Telegraph- 
istes de Londres a very interesting memoir upon the meas- I 
urement of the adhesion which occurs when a voltaic cur- 
rent of a certain intensity is made to pass between two 
metals of the same nature. The author of this remarkable 
paper has also devised a special instrument for the purpose 
of measuring the force necessary to separate the adherent 
metals. It is perhaps not inoppoitune to remark here that 
this adhesion should be considered as a disturbing force in 
many experiments, and especially in telegraphy. The 
measurement of the amount of force required to overcome 
the adhesion gave the following results expressed in 
grammes : 
Copper 
-- 0.15 
Zinc 
11. 
Platinum 
. 42. 
Silver . 
... 0.15 
Tin 
14. 
Iron 
. 85. 
Alluminium ... 
. .. 2.50 
Gold, 
17. 
Steel 
Bronze 
... 8.50 
Lead 
iS. 
Tempered Steel .. 
- 225 
When contact takes place between two different metals, 
the force of adhesion appears to correspond with that of 
the metal requiring the least force for its separation. Thus 
the adhesion of tin with iron would require 14 grammes for 
separation, the corresponding figure for tin, and not that of 
iron, which is 85. The importance of this matter is quite 
obvious, and seems to be well worthy of complete investi- 
gation. On microscopical examination of the two surfaces 
placed in contact, M. Stroh finds that the adhesion always 
arises Irom the fusion of the superficial layer by the elec- 
trical current. — L' Electricite. 
WATER JETS AS A SOURCE OF ELECTRICITY. 
Mr. J. Elster, a pupil of the celebrated Professor 
Quincke, is about to present a thesis, at Leipzig, upon this 
interesting question. The following, according to the 
Journal Philosophique , are the conclusions to which this 
young savant has arrived : 
If any electro-motor force whatever is produced by a jet 
of water, there must have been contact of the particles of 
the water with a solid bod)'. This condition proves that the 
electro-motor force is produced by the friction of the parti- 
cles of water with the metal, so that only a small portion of 
the liquid contributes to the production of electricity. 
Furthermore, when the rapidity of the water jet is in- 
creased or diminished, the effect obtained is proportional to 
the active force of the particles of the liquid, and depends 
also upon the nature of the body placed in contact with the 
water. 
This theory seems to be very similar to that by which ; 
Faraday explained the production of electricity in the Arm- 
strong machine. The conclusions reached by the author are 
opposed to those of many savants, notably the Swedish 
electrician, Ed. Lund. 
1. The movement of a liquid, of itself, cannot produce 
electro-motor force. 
2. The currents called electro-capillary are in the same 
case whether the fluid moistens or does not moisten the 
walls of the tube. In the first case the friction takes place 
between the adherent portion of the liquid and the mole- 
cules in motion. In the second case, the molecules of the 
liquid rub distinctly against the sides of the tubes. 
Finally, his conclusion is that the electro-capillary cur- 
rents, which he claims were discovered by Professor Quincke, 
are identical with the currents developed by friction, which 
have been demonstrated by Zollner on the rubber of electri- 
cal machines. — L' Electricite 1 . 
A NEW ELECTRIC PILE. 
M. Reynier has devised a hydro-electric pile, comparable 
in energy, to the nitric acid couple, without its inconveni- 
ences. The zinc is immersed in a solution of caustic soda. 
The porous cup is made of parchment paper. The new 
couple is about twice as strong as the ordinary Bunsen 
couple, and is surpassed only by the rectangular Bunsen 
couple (after the model of Ruhmkorff). M. Becquerel, Sr., 
has already used a similar pile . — La Science pour Tous. 
TIIE METRIC SYSTEM. 
To the Editor of Science. 
In connection with Prof. Ward’s able “ Plea for the 
Metric System in Microscopy,” in SCIENCE for July 31st, 
it may be well to state that the “ American Metric 
Bureau,” of Boston, 32 Hawley street, has for some 
years been advocating the general use of the system, not 
only by publication of “ The Metric Primer,” and of 
various circulars and bulletins, but in the very practical 
way of supplying standard metric articles at much less 
than ordinary prices. As Prof. Ward well says, “ the 
way to introduce the metric system is to use it ourselves,” 
and judging by the experience of the students in my 
laboratory, who are advised not even to name the anti- 
quated weights and measures, a pocket or desk rule is a 
more convincing argument than exhortation. 
Burt G. Wilder. 
GENERAL NOTES. 
The transformation of alcoholic liquids into vinegar has 
long been a matter of discussion. Pasteur holds that the 
formation of vinegar is a physiological phenomenon caused 
by vegetation of a particular bacterium, the Mycoderma aceti, 
while Liebig sees in it merely a chemical action of oxygen 
on alcohol. Recent observations by Herr Wurm, at the 
Breslau Institute of Plant-Physiology, are regarded as put- 
ting the former view beyond a doubt, and Herr Wurm has 
succeeded in effecting the industrial manufacture of vinegar 
in accordance with Pasteur’s idea. 
Mr. Bissinger, M. E., at Carlsruhe, Germany, gives the 
following results as obtained in his examinations of the 
several motors in regard to their relative cost per horse- 
power for each hour. It will be observed that the examina- 
tion pertained principally to small motors. The relative cost 
per effective horse-power per hour is as follows : 
h.-p. steam engine 7.6 
“ , 44-3 
Lehmann s caloric engine 26.5 
Hock’s motor 40.0 
Otto gas engine ; 26.4 
Otto Lang gas engine 26.4 
Schmidt’s hydraulic motor, supplied with water from the 
city waterworks 95.00 
obtained by horses and a gin 45.00 
obtained by manual labor 200.00 
A calculation of the height of the atmosphere has been 
recently made by Herr Ritter (Wied. Ann.), starting from 
this principle : The quantity of heat which must be commu- 
nicated to a mass of air cooled to absolute zero to bring it, 
under constant pressure equal to the atmospheric, to the 
state of the lowest layer of the atmosphere, is the calorific 
equivalent of the mechanical work which would have to be 
expended to lift this same mass of air from the earth’s sur- 
face to the limits of the atmosphere. Supposing, first, our 
atmosphere to consist of a gas which would retain the proper- 
ties ol a perfect gas to absolute zero, he gets the height 25km. 
Then, making the same calculation for an atmosphere of pure 
water-vapor, he gets 350km. Considering, lastly, that while 
it is hot possible to make an exact calculation for real gases, 
which certainly condense and solidify like water-vapor before 
reaching absolute zero, one must obtain a result little dif- 
ferent from that found in the case of such vapor, he con- 
cludes that the height of our atmosphere must differ little 
from 350km. — a number which agrees well with that deduced 
by Schiaparelli from observation of falling stars. 
According to some recent experiments of M. Goulier, 
the coefficient of expansion by heat of a metal is indepen- 
dent of any pressure put upon the metal, and is the same 
under a tensile strain as under one of compression. 
