Chemistry and Phystes. 259 
molecules in metals quite corresponding to that established for 
transparent solids and liquids by the dynamics of dispersion. In 
experiments made about ten years ago, of which a slight sketch is 
publishe d in the Proceedings of the Literary and Philosophical 
Society of a a I found that a plate of zine and a plate of 
copper kept in m metallic connection with one another (by a fine wire 
or otherwise) act electrically upon electrified bodies in Thelé neigh- 
borhood, and upon one ee as they nn if they = of the 
surfaces, and kept in metallic amie with one another, 
exercise a aia attraction rom 
210719 xe m3 grams weight. 
rte if they were allowed ns approach from any greater distance, 
to the distance, D, the work done by their mutual attraction is 
ne Sos a 
2 10-'° x-——___— centimeter grams ; 
which, if D is very ee in pee with D’, is very approxi- 
mately equal to 2% 10-10 ra 
W suppose a pile to be made of a bee number (N--1) of very 
thin plates alternately of zinc and copper, kept in metallic con- 
nection while they are brought toward one another. Let their 
ewer’ in the pile be parallel, with narrow spaces ing. 
or mee ae let the thickness of each metal fine and interven- 
ing space be The whole work done wi 
bia ci 
et ele 
2x10" + XN D 
The phi mass of the pile (if we neglect that of one of the end 
plates) is NADe, where ¢ denotes the mean of the densities of zine 
and copper. Hence, if h be ae height to which the whole mass 
mee be raised against a constant force equal to its weight at the 
earth’s surface, to do the same amount of work, we have 
NADph=2X 10-19 XN 3 ; 
which gives reo 2X pate oh 
or, as e=8, nearly ae for the nr rough estimate, 
ee 
