a metal bob at the end of a sounding line
Depth sounding, often simply called sounding, is measuring the depth of a body of water. Data taken from soundings are used in bathymetry to make maps of the floor of a body of water, such as the seabed topography. Soundings were traditionally shown on nautical charts in fathoms and feet. The National Oceanic and Atmospheric Administration (NOAA), the agency responsible for bathymetric data in the United States, still uses fathoms and feet on nautical charts. In other countries, the International System of Units (metres) has become the standard for measuring depth.
A sounding lead is a tool used in marine navigation to determine the depth of water. It consists of a heavy lead or weight attached to a long line marked at intervals. This device is dropped into the water and when it hits the bottom, the depth can be determined by examining the markings on the line. This process is known as sounding.
Dictionary of Nautical Terms
An instrument for discovering the depth of water; it is a tapered cylinder of lead, of 7, 14, or 28 lbs. weight, and attached, by means of a strop, to the lead-line, which is marked at certain distances to ascertain the fathoms. (See hand-line.)--Deep-sea lead. A lead of a larger size, being from 28 to 56 lbs. in weight, and attached to a much longer line. (See deep-sea line.)--To heave the lead. To throw it into the sea as far ahead as possible, if the ship is under way.
The numerical value of sounding lead in Chaldean Numerology is: 2
The numerical value of sounding lead in Pythagorean Numerology is: 8