'Casting the Lead'

Hullo there,
I am interested in naval history and have read many books on the subject… Hornblower ect. I’ve never been able to figure out what is meant by ‘casting the lead’ or how it is done. I know it is a way of judging depth under the keel and around the ship but other than that i’m well puzzled. Cheers.

I saw a reconstruction of this on a TV documentary covering a re-enactment of Cook’s voyage.

Essentially there’s a long thin heavy lead weight on the end of a knotted rope; it is thrown into the water in order to measure the depth. There must be quite an art to doing it though because the ship was under sail when it was done; the weight was thrown forward to (I assume) partly compensate for this.

I’ve done a bit of searching, but to no avail. I’d guess (with reasonable certainty) that it refers to the casting out of a plumb line to ascertain depth (the context that I saw it used related to a pilot).

It may also have depressed/sad/angry connotations when used in a non-nautical sense, but that’s not reliable without backup.

The sounding lead was a line with a lead weight. With the ship at slow speed it was cast forward and let to sink so that it would strike the bottom when the ship was over it and the line vertical. The depth was read from marks on the line.

The lead had a cavity in the bottom where tallow was put so that a sample of the sea floor would come up with it.

There were two sizes of lead lines, one for deeper depths (heavier) called the dipsea (deep sea) lead


here’s another page explaining its use: http://www.navyandmarine.org/ondeck/1800soundinglead.htm
The lead cannot be cast when the ship has significant speed and there is any significan depth. Normally the ship would be hove to before soundings would be taken. When slowly navigating channels or other tricky places two seamen would be placed one on each side of the ship, usually on the shroud channels, and they would both be taking soundings.

My boat draws only 5 ft but I sailed an entire season with the electronic sounder broken and I often had to use a hand lead. Of course, in less than ten feet of water it is quite easy.

Read the Cecil Scott Forester novels about Horatio Hornblower, or The Oxford Companion to the Sea. When I first read “casting the lead” I thought it was pronounced “leed”, because you thre it forward. It’s “led”, of course, since it’s made of that heavy metal. Evidently they didn’t just use a knotted line, but there were markers tied in, and in a certain order.