xlviii GENERAL SUMMARY OF SCIENTIFIC AND 



ens downward there is an exhaustion. With 585 mm. of 

 mercury pressure of water, the barometer standing at 735 

 mm., the vacuum produced was 724 mm., and the consump- 

 tion of water three liters per second. No fall of water is 

 necessary, the pressure being all-sufficient. 



Lippmann has published in cxtenso his important memoir 

 on the relations between electric and capillary phenomena. 

 In it he establishes the following important laws : First, the 

 capillary constant at the surface of separation of mercury 

 and dilute sulphuric acid is a function of the electric differ- 

 ence winch exists at this surface ; and, second, when by me- 

 chanical means a liquid surface is made to change its form, 

 the electric difference of this surface varies in such a way 

 that the superficial tension developed in virtue of the first 

 law opposes the continuance of the movement. These laws 

 he has ingeniously applied, first, to the accurate measurement 

 of capillary constants, hitherto so uncertain ; and, second, to 

 the measurement of electro-motive force by means of his cap- 

 illary electrometer. His ingenious electro-caj^illary motor, 

 which shows the direct conversion of electrical into mechan- 

 ical energy by means of capillarity, is also fully described. 



Terquem has published an historical note, in which he calls 

 attention to the fact that the generally received notion that 

 Faraday was the first to liquefy the gases is incorrect, since 

 Guyton de Morveau in 1799 liquefied ammonia gas in a bath 

 of calcium chloride and snow. 



Exner has made some quantitative experiments on the 

 penetration of liquid films by gases. He finds that the ve- 

 locities of diffusion are directly proportional to the coeffi- 

 cient of absorption of the gas for the liquid composing the 

 film, and inversely proportional to the square root of the 

 density of the given gas. Adopting air as the unit of com- 

 parison, the relative velocities are for nitrogen, 0.06 ; oxy- 

 gen, 1.95 ; coal gas, 2.27 ; hydrogen, 3.77 ; carbonous oxide, 

 47.1; hydrogen sulphide, 105; ammonia, 46,000. As to the 

 absolute velocity, Exner finds that 1.88 c. c. of hydrogen and 

 0.55 c. c. of air diffuse simultaneously through each square 

 centimeter of the soapy film. 



G. von Liebig has contrived an exceedingly useful modifi- 

 cation of Frankland's apparatus for gas analysis, in which 

 the measurements arc made, not by measuring the volume 



