Page:Popular Science Monthly Volume 78.djvu/252

242 with the Lucas sounding machine and sounding cups. The machine itself consists of a compact, triple-cylinder, compensating steam engine which turns a reel on which five or six thousand fathoms of steel wire are wound. Geared to the sheave over which the sounding wire runs is a register, which indicates the number of fathoms of wire reeled out.

For depths up to a thousand fathoms, a thirty-five pound shot is used to carry the wire down, and for greater depths a shot of sixty pounds. The shot are perforated with a two-inch hole so that they may be slipped over the cylindrical brass sounding cup. This trips automatically on striking the bottom, dropping the shot, while the sounding cup itself sinks into the mud and brings up an ounce or two as a sample, with the shells and hard remains of countless tiny animals which have played so great a part in the formation of many of the present land masses of the