30 
CALORIC. 
It is owing to the different conducting powers of 
minerals that they occasion different sensations 
when touched. Thus a piece of topaz or rock- 
crystal can be distinguished from a piece of polish- 
ed limestone by its colder feel. " The method of 
making ice and cooling water in hot climates de- 
pends on the principles of the conduction of heat. 
In the European settlements of Bengal, on the 
banks of the Ganges, the cold is so slight that even 
during the winter, which lasts about six weeks, 
there is no fire kindled in any house except for culi- 
nary purposes. Ice is procured from the neighbour- 
ing mountains, and the natives have a peculiar 
method of producing it in larger quantities. They 
dig pits in the earth, lay straw in them, and set 
round uncovered vessels of burned earth on it. The 
vessels are filled with water, and, after sundown, 
small pieces of ice are thrown in : the next morn- 
ing, before sunrise, the vessels, the water in which 
is frozen, are removed." On the same principle, 
water or wine is cooled by wrapping vessels round 
with a wet cloth and placing them in the sun ; evap- 
oration of the fluid soon reduces the temperature 
of the contents of the vessel. 
We clearly perceive the wisdom and goodness 
of Providence, in imparting to bodies gradations of 
power to conduct heat, in the case of snow and ice. 
Were it not for the protection of snow, which is a 
poor conductor of caloric, winter grain and grasses 
would inevitably be killed, and in northern lati- 
tudes the earth would be frozen to such a depth 
that the heat of summer would not be able to thaw 
it sufficient for the purposes of cultivation. 
It is a physical law, to which Dr. Lardner states 
there is no real exception,* that heat expands all 
* In baking bricks it has been supposed that there was an 
exception to this law that heat expands all bodies, as the brick, 
when baked, occupies smaller space than before. But this is 
owing to the expulsion of the water by the heat ; so that we 
