it is more apt to become contaminated with lead from roofs, gutters, cisterns, and water pipes. To purify rain water and render it useful, for the delicate purposes of chemical experiment, Morveau recommends dropping into it a little barytic water

and then exposing it for some time to the atmospheric air. This combines with the carbonic acid, which being the solvent of the carbonate of lime, both it and the carbonate of baryta are precipitated as insoluble salts. Instead of exposing it to the

atmosphere, it may be poured from one vessel to another ; by which means not only the minute portion of barytic water is dispersed through the rain water, and

brought into contact with the carbonic acid, but it involves a great portion of air in its substance, which improves both the taste and the utility of the fluid.

Snow water, as we have already stated, is destitute of air and other gaseous matters found in rain. According to Liebig, it contains ammonia. It has long been a popular, but erroneous opinion, that it was injurious to health, and had a tendency to produce bronchocele. But this malady occurs at Sumatra, where ice and snow are never seen ; while, on the contrary, the disease is quite unknown in Chili and Thibet, although the rivers of these countries are chiefly supplied by the

melting of the snow, with which the mountains are covered. Ice is said not to

quench thirst, but on the contrary to augment it, and that the natives of the Arctic regions prefer enduring the utmost extremity of this feeling, rather than attempt to