SOUNDING, the operation of trying the depth of the water, and the quality of the ground, by means of a plummit stink from a ship to the bottom. For sounding there' arc two plummits used, one of which is called the hand lead, weighing about eight or nine pounds ; and the other, the deep-sea lead, weighing from twenty-five to thirty pounds, and both are shaped like the frustrum of a cone or py ramid. The former is used in shallow waters, and the latter at a great distance from the shore, particularly on approach ing the land lifter a sea voyage. Accord ingly, the lines employed for this purpose are called the deep-sea lead and the hand lead line. The hand-lead line, which is generally twenty fathoms in length, is 'marked at every two or three fathoms, so that the depth of water may be ascertain ed either in the day or night. At the depth of two and three fathoms, there are markt of black leather ; at five fathoms there is a white rag ; at seven, a red rag ; at ten, black leather ; at thirteen, black ; at fifteen, a white rag; and at seventeen, a red rag.
Sounding with the hand-lead, which is called heaving the lead by seamen, is ge nerally performed by a man who stands in the main-chains to windward. Having the line all ready to run out without inter ruption, he holds it nearly at the distance of a fathom from the plummit, and having swung the latter backwards and forwards three or four times, in order to acquire the greater velocity, he swings it round his head, and thence as far forward as is necessary ; so that, the lead's sinking while the ship advances, the line may be almost perpendicular when it reaches the bottom. The person sounding then pro
claims the depth of the water in a kind of song resembling the cries of London hawkers. Thus, if the mark of five fa thoms is close to the surface of the water, he calls, " By the mark five," and as there is no mark at four, six, eight, &c. he es timates those numbers and calls, " By the dip four." [file judges it to be a quar ter or an half more than any particular number he calls, " And a quarter five— and a half four," &c. If he conceives the depth to be three quarters more than a particular number, he calls it a quarter less than the next : thus, at four fathoms and three quarters he calls, " A quarter less five," &c.
The deep-sea lead is marked with two knots at twenty fathoms, three at forty, four at fifty, and so on to the end. It is also marked with a single knot in the mid dle of each interval, as at twenty-five, thirty-five, forty-five, fathoms, &c. To use this lead more effectually at sea, or in deep water on the sea coast, it is usual previ ously to bring-to the ship, in order to re tard her course ; the lead istben thrown as far as possible from the ship, on the line of her drift, so that, as it sinks, the ship drives more perpendicularly over it. The pilot, feeling the lead strike the bottom, readily discovers the depth of the water by the mark on the line nearest is surface.