SIMPLE MINERAL SUBSTANCES. 9 
simple substances as form their constituent parts. Few 
of these, it is true, are to be found in a separate, uncom- 
bined state ; yet that they do exist, and that they are 
to be obtained from the minerals with which they are 
united, we have the proof of every day's experience. 
UNCONFINABLE FLUIDS. 
17. There are some kinds of unconfinable fluids, the 
existence even of which is manifested only by their 
contact with other bodies, or becoming separated from 
them. They are of a nature too subtile to be collected 
or confined in our vessels for the purpose of examina- 
tion, and the investigation of their properties has con- 
sequently been attended with peculiar difficulty. Those 
at present known are caloric, light > electricity r , and mag~ 
netism ; but of these the first only is immediately con- 
nected with the subjects of our present investigation. 
18. Caloric. Every one is acquainted with the dif- 
ferent sensations of heat and cold. That matter which 
produces on our bodies the sensation of heat has the 
name of Caloric; heat being only an effect, of which 
caloric is the cause. This is extended ih a greater or 
less degree through the whole extent of space, and 
penetrates into the interior of even the most solid 
bodies : in so doing it expands the particles of which 
they are composed, augments their bulk, and dimi- 
nishes their solidity. The sun is the principal fountain 
from which the earth is supplied with this fluid ; and it 
passes thence to us at the rate of 1 2,000,0 f miles 
per minute. The defect of caloric in any substance 
occasions the sensation called cold. 
Were the world deprived of caloric, every species of 
organized being would, from that moment, cease to 
B 5 
