30 



CALORIC, 



It is owing to the different conducting powers ol 

 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 



