undercroft (underkroft)

cret pa age under ground. our Fathers, III. 299. undercryt (un-der-krī'), v. t. [ME. undercryen; II. n. 1. A current in a body of water or other liquid, or in the atmosphere, below the upper or superficial currents.-2. Figuratively, something at work below the surface or out of sight, as influence or feeling, which has a tendency opposite to or different from what is visible or apparent. There was a peculiar brightne in her face, due in reality to an under - current of excitement. George Eliot , Mill on the Flo , v. 5. 3. In hydraul, mining, an arrangement on the sluices which is intended to aid in saving the gold. The coarser material is separated from the finer by means of a "grizzly" (a set of iron or steel bars placed about an inch apart in the bottom of the main sluice), and this finer material is carried into the "undercurrent" proper, which is a shallow box of varying shape but very large dimensions, much wider than the main sluice, and paved with blocks, iron rails, or cobbles, thus forming a kind of broad sluice by the side of and beneath the main one, and in the newest arrangements having a considerably steeper grade. The material which escapes from the undercurrent is led back into the main sluice lower down. As many as six, or even more, of these undercurrents are occasionally introduced into the sluice-line.