The Sounding Lead
By James Mathews
The lead is one of the most useful instruments on board ship. We will first consider the hand lead, or blue pigeon, as sailors call it. It’s appearance is as follows:
It is usually seven or fourteen pounds in weight although four, six, eight and ten pound leads are made. The lead weight that I have illustrated in front of me (and the one that I made up in the Navy) was a six-sided lead weight of fourteen pounds (we used a six pound lead for sounding work when I was a Sea Scout on the Columbia River-1951-54). The lead tapers to the top (about 10-12 inches tall) with ring molded into the top of the lead. The line is fastened to the top of the lead with a loose eyesplice, well served. The bottom of the lead is dished deeply (hollowed out to a depth of about 1"-1 ½") and filed with tallow. This is called the arming.
The lead line, for a hand lead, is usually sixty fathoms in length and is made of well-stretched American or Italian hemp, untarred and should be pliable. Before making a lead line, soak it in water and put it on a good stretch, about twice that of the weight of the lead you are using. (When I made mine in the Submarine Service I used about 50# stretch). Seize a small wooden toggle into the line about 2 fathoms from the lead (near the 2 fathom mark) to assist the leadsman in measuring the amount of the leadline to swing..
The markings of the hand lead are as follows:
2 fathoms from the lead; 2 strips of leather;
3 " " " " ; 3 " " " :
5 " " " " ; white cotton rag;
7 " " " " ; red woolen rag;
10 " " " " ; leather with a hole;
13 " " " " ; same as 3 fathoms;
15 " " " " ; same as 5 fathoms;
17 " " " " ; same as 7 fathoms;
20 " " " " ; small line with 2 knots;
25 " " " " ; small line with 1 knot;
30 " " " " ; small line with 3 knots;
35 " " " " ; small line with 1 knot;
40 " " " " ; small line with 4 knots;
and so on, a mark at each five fathoms. These are known as the marks of the lead line. The fathoms not marked are known as the deeps of the leadline, and together we speak of the "marks and the deeps" of the lead line.
Casting the lead
Taking soundings, or casts of the lead, is done when the vessel has headway on, the
leadsman casting the lead forward and getting the depth as the vessel passes over the
lead, resting on the bottom. The method of procedure is as follows:
The leadsman grasps the leadline at the toggle and swings the lead back and forth, parallel with the side of the ship, the leadsman being in a projecting lead stand, or in the chains in a sailing vessel, the lead is sent over head for two full turns and released at the bottom of the swing flying forward at a tangent, and almost parallel with the surface of the water. The motion of the swinging lead is opposite to that of a wheel turning with the motion of the ship. Assuming a right hand throw, from the starboard side, the left hand of the leadsman holds the coils of the line, freely forward, so it can run out without hindrance and without kinks. As the line flows out and the lead reaches the bottom, the leadsman grasps the running line with his right hand and pulls it rapidly plunging it up and down to feel the bottom. Feeling bottom, he plumbs the line up and down as the ship passes by the lead. He bends over and notes the mark above the water. If a mark is directly at the water, he calls out that mark, as "by the Mark five". If slightly under water "Mark underwater, five." If the five is three feet up, ""and a half four", if the five is six feet up," by the deep four." And so on , calling the marks and deeps or the spaces in between. If the mark is seven, for instance, is a quarter fathom out of the water (1.5 ft.) the leadsman would call, "and a quarter less seven." Before the next cast the leadsman will look at the arming and report the state of the bottom and clean the arming for the next cast. This gives you the general idea. The leadsman sings out the marks and deeps. He never uses "sir" as some are apt to do. The soundings should be called out sharp and clear. Leadsmen should practice casting the lead from both starboard and port lead stands.
Water Bag
The water bag is a canvas bag, with a circular bottom, about fourteen inches long and two
inches in diameter, made from #1 canvas, a grommet sewn on the upper edge and a strong
becket spliced into this. It is filled with water and used in place of the lead for
practice casting. If the novice makes a bad cast he will get only a shower, not a crack on
the head with a blue pigeon.
Sounding at Night
The leadsman, working in darkness, must know the distance from his waist to the waterline.
He reads the mark closest to his waist by feel (or in cold weather by touching the mark to
his lips or tongue which are more sensitive than cold fingers) and then subtracts this
distance from his depth. Only the exact water depth is cried to the bridge.
Dipsea
The coasting lead is a large hand lead, sometimes called the deep sea lead (sailors call
it the dipsea) dropped from the bow and weighing fifty pounds. The line is about 120
fathoms. The method of using the dipsea lead is as follows:
Station a reliable man on the forecastle head with the lead and a length of line coil in hand, say 10 fathoms. At intervals along the side of the ship at about every hundred feet, have a man with a similar coil of line, the bight being placed outside and clear of all projections, The last man, with the last coil in a tub, clear for running and fastened securely inboard, the man well clear of the line, stands at the taffrail to take the reading of the cast. Since all leads are hollowed in the botom and armed with tallow, as the lead strikes the bottom, it will gather and bring up a sample of the botom like pebbles, sand, speckled shell, blue mud or chalk. All these things and many more can be added to the chart and together with the depth greatly aid in locating a vessel at night or in the fog when soundings are taken.