104 C. Barus — Repulsion of Two Metallic Disks. 



10 3 AiT = 18cm., Wd = 64cm., /= 1-17 dynes 



the results of /' and d as shown by the cross in fig. 6 fit in very 

 well with the present data obtained from electric attraction. 

 The repulsion therefore has throughout been found of the 

 same order of values. 



Probably the most interesting feature of these molecular 

 atmospheres will be their bearing on the nature of voltaic con- 

 tact. We may compute the pressure corresponding to the 

 thrust f\ as above, by dividing by the area A of the disks, 

 whence jp =f/3%4:. We may then estimate the attraction of 

 the disks per gram of air couche, at a distance h from the disk, 

 similarly to the ordinary case of the barometric formula : 



-dp = (p/Rr)B(h)dh or - Erd(\og f)/dh = F(h), 



R, being the gas constant, r the absolute temperature. Thus 

 if one can detect the variation of f with A, the molecular 

 attraction of the disk per gram of air should be discernible. 

 One may anticipate its variation for different metals. 



Brown University. 



Providence, R. I. 



