the measure of any thing from the surface downwards.

Measuring of Depths by the Barometer, depends on the same principles on which heights are measured by the same instrument. The mensuration of depths being chiefly applied to mines, is still more precarious than the mensuration of heights, on account of the various kinds of vapours with which the subterraneous regions are filled. But for a particular account of these difficulties, with the best methods of obviating them, see BAROMETER and MINES.

DEPTH of a Squadron or Battalion, is the number of men in a file; which in a squadron is three, and in a battalion generally six. See SQUADRON, FILE, &c.

We say, the battalion was drawn up fix deep; the enemy's horse was drawn up five deep.

DÉPURATION, is the freeing of any fluid from its heterogeneous matter or scumulence. It is of three kinds; 1. Decantation; which is performed by letting the liquor to be depurated stand for some time in a pretty deep vessel, till the gross sediment has fallen to the bottom; after which the clear fluid is poured off. 2. Despumation; which is performed by means of the whites of eggs, or other viscid matter, and is also called CLARIFICATION. 3. Filtration; which is effected by passing the fluid through cloth or porous paper.