Sounding Line

The Lead Line -- Construction and use

by Allen Mordica, TMLHA
(photos: USNLP)

Two leads are employed on vessels: the deep sea lead weighing 28 lb., and the hand lead weighing 14 lb. (a lead weighing somewhat less is sufficient for a small boat). We will look at a small, easily constructed line suitable for instructional and light duty use.

To prepare a lead line, assemble the strips of material, a 3-8 lb. lead weight, and 25 fathoms (150 ft.) of 3/8" cotton or manila line. (A note on the sinker; I was unable to obtain a lead, and so was required to cast my own. I carved each half of the mold from pine 2x12's, and the resulting weight didn't look half bad.) Splice the eye of the weight to one end of the line. If you want to allow for hollow in the heel of the lead (see below), flatten the base of the lead with a hammer or, on a large lead, saw off the base flat with a hacksaw, then drill a shallow hole for the tallow (also see below) in the center of the base. At each appropriate point, measured from the weighted end, use a fid or marlinspike to open the strands of the line. Insert the appropriate strip of material, so that the strip extends equally from both sides of the line, then allow the strands to return to their normal position, trapping the strip in the line. Then place whipping immediately at either side of the mark to help hold the strands tightly in place. The line used for a hand lead is 25 fathoms long, and is generally marked as follows:

At 2 fathoms-....Leather, with two lobes.(should look like a flat Milk-Bone biscuit)
3 ".........Leather, with three ends (like above, with 3 "lobes" at each end)
5 ".........White calico. (2" wide x 6"long strip)
7 ".........Red bunting. (same size as above)
10 "........Leather, with hole through it at each end.(same as above)
13 "........Blue serge.(same as above)
15 "........White calico.(same as above)
17 "........Red bunting.(same as above)
20 "........Strand of light line, with two knots in it at each end.

It is possible, by the different feel of the materials used, to tell what mark is in one's hand in the dark. The above depths are called marks; the unmarked depths in fathoms are called "the deeps".

Thus, at five fathoms, the leadsman calls, " By the mark five," in eleven fathoms,"By the deep eleven." He also calls halves and quarters of fathoms i.e.," And a half six,'' for six and a half fathoms, "A quarter less six," for five and three-quarters.

To take soundings while under way, the leadsman would take his place at the bow of a small boat, or at the forward chain plates on a large ship, secured from falling overboard by a "breast band", a wide strip of canvas used like a seat belt tied between two shrouds. The leadsman could then lean forward against the band to swing his lead in the clear. He would then swing the lead round and throw it as far forward as possible, so that the lead would be resting on the bottom and the line tight, when the vessel is directly over the lead.

If the lead is hove properly, so that the line pays out with a little tension as it passes through the hands, it is easy to tell when it has reached the bottom by the sudden slack felt in the line. When sailing in shoal waters, soundings can be taken much quicker with a pole or boathook than with a lead.

There is a hollow at the base, or "heel" of the lead which can be filled, or "armed", with tallow; a specimen of the bottom (mud, sand, or shingle) is brought up with the lead, and this, by referring to the chart, which generally marks the nature of the bottom, may help find your position precisely.