40  W. Thompson on the size of Atoms. 
till they are parallel and at a distance of a hundred-thousandth 
of a centimeter asunder. In this position they will attract one 
another with a force equal in all to two grams weight. By 
stract dynamics and the theory of energy, it is readily proved 
that the work done by the changing force of attraction during 
the motion by which we have supposed this position to be 
reached, is equal to that of a constant force of two grams 
weight ‘acting through a space of a hundred-thousandth of a 
centimeter; that is to say, to two hundred-thousandths of 
a centimeter-gram. Now let a second plate of zine be brought 
y a similar process to the other side of the plate of copper; 
a second plate of copper to the remote side of this second plate 
of zine, and so on till a pile is formed consisting of 50,001 plates 
a centimeter thick. The whole work done by — attrac- 
tion in the formation of this pile is two centimeter-gram 
The whole mass of metal is eight grams. — the eset 
of work is a quarter of a centimeter-gram per gram of metal. 
Now 4,030 centimeter-grams of work, Ho -ng to Joule’s 
dynamical equivalent of heat, is the —— required to 
warm a gram of zine or copper b e degree centigrade. 
Hence the work done by ae electric an could warm 
the substance by only ystzs of a degree. But now let the 
thickness of each piece of sate and of each intervening space 
be a hundred-millionth of a centimeter instead of a hundred- 
thousandth. The work would be i increased a million-fold un- 
enough to e the temperature of material by 62°. This 
is barely, if po tall admissible, according to our present knowl- 
edge, or, rather, want of poi regarding the heat 
ne 
hundred-millionth of a centimeter. The work and its heat 
equivalent will be increased» sixteen-fold. It would there- 
fore be 990 times as much as that required to warm the mass 
by 10 cent, which is very much more’ than can possibly be 
roduced aq and copper in entering into molecular com- 
bration r 
