( Chiefly compiled from the works of Thomson, Pereira, Whewell and others.)

Water was regarded by the ancients as an elementary substance, and as a constituent of most other bodies. This opinion was somewhat modified by the experiments of Van Helmont and Mr. Boyle, who maintained that it could be changed into all vegetable substances, as well as into earth ; but it was substantially held until the middle of the last century, (1781,) when Mr. Cavendish proved that this liquid was a compound of oxygen and hydrogen.

Natural History. In the inorganized kingdom.

Water is very generally diffused over the surface of the globe, forming seas, lakes, and rivers ; it is mechanically disseminated among rocks, constitutes an essential part of some minerals, and always exists to a greater or less extent, in the atmosphere. In the air, water is formed in two states ; as a vapor (which makes about

one-seventieth by volume, or one one-hundreth by weight of the atmosphere) it is

supposed to be the cause of the blue color to the sky ; and in a vesicular form, in which state it constitutes the clouds. Terrestrial water forms about three-fourths of

the surface of the terraqueous globe. The average depth of the ocean is calculated at between two and three miles. Now as the height of dry land above the surface of the sea is less than two miles, it is evident, that if the present dry land were distributed over the bottom of the ocean, the surface of the globe would present a mass