SOUNDING

There are two plummets used for this purpose in navigation; one of which is called the hand-lead, weighing about 8 or 9 pounds; and the other the deep-sea-lead, which weighs from 25 to 30 pounds,. and both are shaped like the frustum of a cone. or pyramid. The former is used in shallow waters, and the latter at a great distance from the shore; particularly on approaching the land, after a sea-voyage. Accordingly the lines employed for this purpose are called the deep-sea-lead-line, and the hand-lead-line.

The hand-lead-line, which is usually 20 fathoms in length, is marked at every 2 or 3 fathoms; so that the depth of the water may be ascertained either in the day or night. At the depth of 2 and fathoms, there are marks of black leather; at 5 fathom, there is a white rag; at 7, a red rag; at 10, black leather; at 13, black leather; at 15, a white rag; and at 1, a red ditto.

Sounding with the hand-lead, which is called heaving the lead by seamen, is. generally performed by a man who stands in the main-chains to windward. Having the line all ready to run out, without interruption, he holds it nearly at the distance of a fathom from the plummet, 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, by. the lead's sinking whilst the ship advances, the line may be almost perpendicular when it reaches the bottom. The person founding then proclaims the depth of the water in a kind of song resembling the cries of hawkers in a city. Thus, if the mark of fathoms is close to the surface of the water, he calls 'By the mark five!' and as there is no mark, at 4, 6, 8, &c. he estimates those numbers, and calls, 'By the dip four,' &c. If he judges it to be a quarter, 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 quarters more than a particular number, he calls it a quarter less than the next: thus, at four fathom and 3/4, he calls 'A quarter less five!' and so on.

The deep-sea-lead is marked with two knots at 20 fathom, 3 at 30, 4 at 40, and so on to the end. It is also marked with a single knot in the middle of each interval, as at 25, 35, 45 fathoms, &c. To use this lead more effectually at sea, or in deep water on the sea-coast, it is usual previously to bring to the ship, in order to retard her course: the lead is then 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 its surface. The bottom of the lead being also well rubbed over with tallow, retains the distinguishing marks of the bottom, as shells, ooze, gravel, &c. which naturally adhere to it.

The depth of the water, and the nature of the ground, which is called the soundings, are carefully marked in the log-book, as well to determine the distance of the place from the shore, as to correct the observations of former pilots. See COASTING and NAVIGATION.

Reference Works