the view on the right shows the depression where tallow was placed to pick up sea-bed sediments to aid navigation

sounding lead

Navigational sounding weight, called a lead, or sounding lead. Made of cast lead, weight 7lb. Length 8", 1 1/2" square, eyehole in top for attachment of rope.

curator's notes
Lead and line, a method of depth sounding used on boats and ships.

BRXHM reference: 5378.1