leadsman

leads·man

 (lĕdz′mən)
n. Nautical
The person using the lead line in taking soundings.
American Heritage® Dictionary of the English Language, Fifth Edition. Copyright © 2016 by Houghton Mifflin Harcourt Publishing Company. Published by Houghton Mifflin Harcourt Publishing Company. All rights reserved.

leadsman

(ˈlɛdzmən)
n, pl -men
(Nautical Terms) nautical a sailor who takes soundings with a lead line
Collins English Dictionary – Complete and Unabridged, 12th Edition 2014 © HarperCollins Publishers 1991, 1994, 1998, 2000, 2003, 2006, 2007, 2009, 2011, 2014

leads•man

(ˈlɛdz mən)

n., pl. -men. Naut.
a person who sounds with a lead line.
[1500–10]
Random House Kernerman Webster's College Dictionary, © 2010 K Dictionaries Ltd. Copyright 2005, 1997, 1991 by Random House, Inc. All rights reserved.
References in periodicals archive ?
It comes from the leadsman's call by the deep six for a depth corresponding to the sixth deep on a sounding line.
Type loc.: South Africa, KwaZulu-Natal, Leadsman Shoal, -100 m, dredged A.
Type loc.: South Africa, KwaZulu-Natal, Leadsman Shoal (ca 27[degrees]47'S 32[degrees]39'E), -100 m, dredged [A.
This was accomplished by a leadsman throwing a lead weight attached to a line overboard to measure the water's depth.
(24) One of Budd's theories is similar to Kahn's in that he notes Twain showed "an interest in Jewish lore during his stay in Austria [1898], and he could have picked up forty-four as a name for a quasi god that existed prior to the Old Testament fall of Adam and Eve." Rasmussen theorizes that "Twain may have seen it as an abbreviated form of 144, the highest number in the standard multiplication table." Another of his theories is that the "number 144 is suggestive because there are 12 feet, or 144 inches in two fathoms--the nautical depth equivalent to the steamboat leadsman's measurement of 'Mark Twain'" (Schidt).
Samuel Clemens was a young steersman on the Mississippi, and from that experience took the pen name Mark Twain, from the leadsman's call meaning 12 feet of water and safe going.
When the leadsman detected a depth of only 12 feet he would sound the alert: 'By the maaa-ark, twain!' His writing under this name earned him international renown as a writer, lecturer and traveller, through the creation of chracters like Tom Sawyer and Huckleberry Finn.
The old-time pilot's memory does its work "unconsciously," effortlessly laying up "its vast stores, hour by hour, day by day." Though attending to other things, he notes the leadsman's call of "quarter twain" in the midst of a seemingly endless series of "half twain" calls.
Herbert, 18-26.x.1986 (D5298); Leadsman Shoal, outer portion (27.80[degrees]S 32.62[degrees]E), -24-26 m, sorted from stone washings, D.
dived, 7&12.v.1990 (S1674); Leadsman Shoal, Raggie Reef, 1-2km North of Leven Point (27.90[degrees]S 32.62[degrees]E), -9-14 m, mixed algal and coral reef, D.
NMDP, 12.vi.1988 (NMSA E5196); 1 sh., Leadsman Shoal, Raggie Reef, -8-14 m, a mixed algal and coral reef, 1-2 km north of Leven Point, sorted from stone washings (NMSA E2726); 5 sh., Mapelane (NMSA E1662); 6 sh., Mission Rocks, N of St Lucia (J.P.