Chemical Effects of Caloric, $c. 59 



was required to burst the globe in this state was 

 computed at upwards of 27,000lbs. Boyle says 

 the expansion of water in freezing is about an 

 8th or 9th of its bulk. The bursting of leaden 

 pipes placed near or within the earth's surface 

 proceeds from the same cause. The pavement 

 even suffers from the frost, which swells the earth 

 and loosens the stones; nay, rocks have been 

 known to burst in frosty weather. Frost is by 

 some supposed to fertilize, by loosening the co- 

 hesion of the particles of earth. 



As ice is never clear or transparent, and as 

 we find several cavities in it, some have thought 

 that the air insinuates itself, and in this way have 

 endeavoured to account for the expansion. But 

 this has been refuted by water being frozen under 

 an exhausted receiver, and the same cavities being 

 found in the ice; the ice, indeed, instead of being 

 heavier, was lighter, and floated on the water. 

 M. D. Mairan at length solved the difficulty. 

 He says, the particles of water in freezing assume 

 a different arrangement, are not in so close con- 

 tact, and cut each other at angles of 60". If this 

 is the case, then, as indeed is now generally 

 agreed, we cannot say with propriety that the 

 solid particles of water expand, but that from 

 their crystallization into the form of ice they re- 

 quire more room, or occupy a greater space. 



As salts are observed in crystallization to put 

 on regular figures, it was thought that the star- 

 like appearance of snow was owing to a salt 



