DISTILLATION OF WATER. 



357 



inseparable from the liquid otherwise. When it is desirable to distil large 

 quantities of water a larger apparatus is used, called an " Alembic.'*' The 

 principle is simply to convert the liquid by heat into vapour, then cool it, 

 by condensation, in another vessel. 



The evaporation of water, with its effects upon our globe, belong more 

 to the study of Meteorology. 



Rain-water is the purest, as we have said, because it goes through the 

 process of distillation by nature. The sun takes it up, by evaporation, into 



Fig. 348. Distillation. 



the air, where it is condensed, and falls as rain-water. Water containing 

 carbonate of lime will petrify or harden, as in stalactite caverns. The car- 

 bonic acid escapes from the dripping water, the carbonate in solution is 

 deposited as a stalactite, and finally forms pillars in the cave. Sea-water 



