32 
CALORIC. 
perceive that the form of bodies is dependant on 
heat. By its increase solids are converted into li- 
quids, and liquids are dissipated in vapour; by its 
decrease vapours are condensed into liquids, and 
these become solid. If matter ceased to be under 
the influence of heat, all liquids, vapours, and, doubt- 
less, even gases, would become permanently solid, 
and all motion on the surface of the earth would be 
arrested.* 
Now, as there is a continual change of tempera- 
ture in all bodies on the surface of the globe, it fol- 
lows that there is a continued change of magnitude. 
The substances surrounding us are constantly swell- 
ing and contracting under the vicissitudes of heat 
and cold. They grow smaller in winter and larger 
in summer. They swell their bulk in a warm day 
and contract it in a cold one. Thus we see that in 
warm weather the flesh swells and the vessels ap- 
pear filled ; in cold weather the flesh contracts, the 
vessels shrink, and the skin shrivels. 
When water freezes it becomes lighter, and 
therefore swims ; were it not for this circumstance, 
our lakes and rivers would all become solid bodies 
of ice during the winter. Caloric is given from 
substances when freezing, which tends to mitigate 
the severity of cold. For this reason we feel 
warmer after a heavy fall of snow. Ice thaws 
very gradually ; were it not so, the most alarming 
inundations would follow. 
Heat is measured by means of the thermometer. 
This is merely a graduated glass tube, containing 
quicksilver, alcohol, or other substances which do 
not readily freeze. After the fluid is introduced, 
the air is expelled by heating the bulb, when the 
tube is hermetically sealed ; then, by immersing it in 
boiling water, the mercury rises to a certain point, 
which is marked; afterward it is immersed in a 
* Turner's Chemistry. 
