242 OBSERVATIONS ON THE NATURE OF HEAT. 
no two bodies can occupy the same space in the same moment of time. 
For example, if a piece of wood or metal be plunged into a vessel fill- 
ed to the brim with water, a portion of the water will overflow, exactly 
equal to the bulk of wood or metal immersed. To apply the same 
experiments to caloric, with our present knowledge of its nature, 
would be impossible ; but there is evidently something very analogous, 
as is shewn in the following experiment by the distinguished 
chemist Berthollet :—‘ He took pieces of gold, silver, copper, and 
iron, equal in size, and submitted them to the stroke of a coining 
press when he ascertained the heat produced by each stroke, by 
throwing the pieces into water, the relation between the degree of 
heat given to the water, and the heat previously in the metal having 
been found by experiment.” So he was able to ascertain how much 
the temperature of each piece had been raised; and the conclusions 
are these: each piece gave the greatest quantity of caloric out at the © 
first stroke, less at the second, and still less at the third ; besides, 
there was a close connection between the caloric produced by each 
blow and the reduction in size of the metal. Now, from these facts, 
I think, we may fairly infer the point at issue. Each piece of metal 
underwent the greatest diminution, and gave off the greatest quantity 
of caloric at the first stroke ; there was less diminution and less 
caloric, at the second stroke ; and still less of these at the third 
stroke. The particles or atoms of the metal would, on the first 
stroke, approach nearer to each other, whereby something, if any 
thing existed between the particles, must be thrown out, and that 
something may be caloric, which the increase of temperature seems 
to support. After the first stroke, the distance between the particles 
would be less, consequently there must be less of any thing be- 
tween them; hence less contraction and less of anything to thrust 
out on the second stroke; and so with the third stroke. This 
argument may be met by saying, that there is no caloric in cold 
metal, at least not so much as to explain the quantity that can be 
produced in percussion. Our senses, or the most delicate thermo- 
meter, indeed, cannot inform us of the actual quantity of caloric in 
any body. The information these give us is only relative, and our 
knowledge of the subject has been compared to a person knowing a 
few links in the middle of a chain, while the extremities are removed 
from his view. So in the metal there may be much caloric, not to be 
detected by our senses or our instruments, capable of being evolved 
on compression, as the latent heat of steam is evolved on the con- 
densation of the same. JI am aware that, in hazarding this remark, 
