8 4 



SCIENCE. 



TRANSLATIONS. 



M. Stroh presented to the Socicte" des Ingenieurs Telegraph- 



istes dc Londres a very interesting memoir upon the meas- 

 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 

 me:als. 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 

 .. 0.15 

 ... 2.50 

 -- 8.50 







Platinum 



Iron 



- 42 



- 85 



Tin 



Gold 

 Lead 



14. 



17. 



.... 18. 



Alluminium 

 Bronze 



Steel 



Tempered Steel .. 



100 

 - 22 . 



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.— U 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 body. 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- 

 ( ules 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 (hums were discovered by Professor Quincke, 

 are identical with the currents developed by friction, which 

 have be< n demonstrated by Zollner on the rubber of electri- 

 cal mat nines. — L EUctriciti. 



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 i 1 - immersed in a solution of caustic soda. 

 The porous c up is made of parchment paper. The new 



COUple is about twice as strong as the ordinary Huusen 



couple, and is surpassed only by the rectangulai Bunsen 

 ( ou pic (aftei tin- model of Ruhmkorff), M Becquerel, Sr., 

 has already used a similar pile. — I.u Science pour Tous. 



THE 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 Havvley 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 : 



100 h.-p. steam engine _ 7.6 



2 " , " , •— 44-3 



2 " Lehmann s caloric engine 26.5 



2 " Hock's motor _ _ 40.0 



2 " Otto gas engine 26.4 



2 " Otto Lang gas engine 26.4 



2 " Schmidt's hydraulic motor, supplied with water from the 



city waterworks 95.00 



2 " obtained by horses and a gin 4500 



2 " obtained by manual labor 200.00 



A CALCULATION of the height of the atmosphere has been 

 recently made by Herr Ritter (IVied. Aim.), 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 ot a pel led 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 not 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 agues well with that deduced 

 by Schiaparelli from observation of falling stars. 



According to some recent experiments of M. Goulier, 

 tin 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 undei one of compression. 



