230 Intelligence and Miscellaneous Articles. 



the electroscope, for otherwise the entire amount of the difference 

 of potential due to 144 elements is not produced in the electroscope. 



"When no current could be ascertained in the battery, even with 

 a reflecting-galvanometer which gave ten-millionths of an am- 

 pere, the above condition seems to have been fulfilled. For if one 

 pole was insulated, and the other connected with an electroscope, 

 and if it was charged with an ebonite rod, an instantaneous dis- 

 charge took place, when the insulated pole was put to earth. 



The small divergence of the gold leaves was determined with 

 sufficient certainty by viewing it at a distance of 1*605 metre with 

 a powerfully magnifying spectrometer-telescope, the micrometer- 

 screw of which was provided with a milled head divided into 100 

 parts, in which six parts represented a minute. As a mean of 

 several values, the smallest of wmich differed from the largest by 

 about 4 per cent, the number of divisions was found to be 12*9 ; so 

 that a?= 0-1004 centim., and thus = 240*0. By the aid of the 

 electroscope used and of the formula 



P=0V3-285^+3-O32ar, 



or, still better, of a curve on coordinate paper, differences of poten- 

 tial of considerable amount may be determined with an error 

 amounting to perhaps 5 per cent., in which, instead of reading by 

 projection, the far simpler method of reading by a glass micrometer 

 in the eyepiece of the telescope may be used. The upper limit of 

 the differences of potential to be ascertained may be determined by 

 means of an electroscope with heavy leaves. 



I might mention, in conclusion, that in the absence of a 

 Beetz's dry pile, <f) might be ascertained if the deflection of an elec- 

 troscope connected with a Leyden jar is noted, when the jar is 

 discharged with a given length of spark. For this the knowledge 

 of the difference of potential corresponding to a given striking dis- 

 tance is required. An experiment gave a very close agreement for 

 the value p. — Wiedemann's Annalen, No. 7, 1886. 



APPLICATION OF THERMODYNAMICS TO CAPILLARY PHENOMENA. 

 BY P. DUHEM. 



Gauss and Laplace have founded a theory of capillary phenomena 

 on molecular considerations, in which they assume that the forces 

 with which the smallest parts act on each other possess a function 

 of force in the ordinary mechanical sense. Poisson and several 

 others have shown that this theory holds also when the density 

 near the surface varies ; the first supposition has been generally 

 adopted. 



This, however, is no longer admissible if we are compelled to 

 take into account virtual displacements which changes of tempera- 

 ture bring about, and such changes of temperature, as Thomson has 

 shown, are in general necessarily connected with changes of the 

 capillary surface. 



