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If the depth was at a mark he would call "by the mark" followed by the number, while if it was between two marks, he would call "by the deep" followed by the estimated number; thus "by the mark five", since there is a five-fathom mark, but "by the deep six", since there is no six-fathom mark. Fractions would be called out by preceding the number with the phrases "and a half", "and a quarter", or "a quarter less"; thus 4 3/4 fathoms would be called as "a quarter less five", 3 1/2 as "and a half three", and so on. Where the depth was greater than 20 fathoms the line would commonly be marked with a single knot at 25 fathoms, two knots at 30, and so on.
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321:) and a spring-loaded wooden pulley block (the nipper). Again, the device was designed to operate alongside a lead and line. In this case, the buoy would be pulled behind the ship and the line threaded through the pulley. The lead could then be released. The buoy ensured that the lead fell perpendicular to the sea floor even when the ship was moving. The spring-loaded pulley would then catch the rope when the lead hit the sea bed, ensuring an accurate reading of the depth.
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333:(Lord Kelvin) and patented in 1876. This operated on the same principle as lead and line sounding. In this case, the line consisted of a drum of piano wire whilst the lead was of a much greater weight. Later versions of Kelvin's machine also featured a motorised drum in order to facilitate the winding and unwinding of the line. These devices also featured a dial which recorded the length of line let out.
305:. The machine was designed to be fixed to a sounding lead and line. It featured a rotor which turned a dial as the lead sank to the sea floor. On striking the sea floor, the rotor would lock. Massey's sounding machine could then be hauled in and the depth could be read off the dials in fathoms. By 1811, the Royal Navy had purchased 1,750 of these devices: one for every ship in commission during the
276:. If the plummet came up clean, it meant the bottom was rock. Nautical charts provide information about the seabed materials at particular locations. Nautical charts also include depth contour lines. It is thus sometimes possible to navigate in poor visibility by noting which contour line one is closest to.
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and other materials, and so shaped and attached that it is possible to "read" them by eye during the day or by feel at night. Traditionally the marks were at every second or third fathom: at 2, 3, 5, 7, 10, 13, 15, 17, and 20 fathoms. The "leadsman" called out the depth as he read it off the line.
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Both Massey and Burt's machines were designed to operate in relatively shallow waters (up to 150 fathoms). With the growth of seabed telegraphy in the later nineteenth century, new machines were introduced to measure much greater depths of water. The most widely adopted deep-sea sounding machine in
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Massey's was not the only sounding machine adopted during the nineteenth century. The Royal Navy also purchased a number of Peter Burt's buoy and nipper device. This machine was quite different from Massey's. It consisted of an inflatable canvas bag (the
672:, devised a visual indicating device for measuring relatively short time intervals and by which shoal and deep depths could be registered. In 1925, the C&GS obtained the very first Fathometer, designed and built by the Submarine Signal Company.
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in
Britain, were concerned about the reliability of lead and line sounding. The introduction of new machines was understood as a way to introduce standardised practices for sounding in a period in which naval discipline was of great concern.
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in the 1850s, the leadsmen also used old-fashioned words for some of the numbers; for example instead of "two" they would say "twain". Thus when the depth was two fathoms, they would call "by the mark twain!". The
American writer
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in a concavity at the bottom of the plummet. The tallow would bring up part of the bottom sediment (sand, pebbles, clay, shells) and allow the ship's officers to better estimate their position by providing information useful for
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A Mathematical and
Philosophical Dictionary: Containing an Explanation of the Terms, and an Account of the Several Subjects Comprized under the Heads Mathematics, Astronomy, and Philosophy both Natural and Experimental (Volume
363:(literally "fathom measurer"), which determined water depth by measuring the time required for an echo to return from a high-pitched sound sent through the water and reflected from the sea floor, was invented by
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During the nineteenth century, a number of attempts were made to mechanise depth sounding. Designs ranged from complex brass machines to relatively simple pulley systems. Navies around the world, particularly the
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has largely replaced the sextant and chronometer to establish one's position at sea, but many mariners still carry a sextant and chronometer as a backup. Many small craft still rely solely on a sounding line.
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At sea, in order to avoid repeatedly hauling in and measuring the wet line by stretching it out with one's arms, it is common practice to tie marks at intervals along the line. These marks are made of
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Measuring the depth of water by lead and line dates back to ancient civilization. It continues in widespread use today in recreational boating and as an alternative to electronic
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has increasingly displaced both of those methods. A sounding line can still be found on many vessels as a backup to electronic depth sounding in the event of malfunction.
176:, at its end. Regardless of the actual composition of the plummet, it is still called a "lead". Leads were swung, or cast, by a leadsman, usually standing in the
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navigators are known to have used sounding leads, some of which have been uncovered by archaeologists. Sounding by lead and line continued throughout the
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Traditional terms for soundings are a source for common expressions in the
English language, notably "deep six" (a sounding of 6 fathoms). On the
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571:"Sounding in silence: men, machines and the changing environment of naval discipline, 1796-1815 (free PDF available online)"
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Both lead-and-line technology and sounding machines were used during the twentieth century, but by the twenty-first,
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Hohlfelder, R., ed. (2008). "Testing the Waters: The Role of
Sounding-Weights in Ancient Mediterranean Navigation".
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In answer to the need for a more accurate depth registering device, Dr. Herbert Grove Dorsey, who later joined the
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One of the most widely adopted sounding machines was developed in 1802 by Edward Massey, a clockmaker from
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Dunn, R (2012). "'Their brains over-taxed': Ships, Instruments and Users". In Dunn, R; Leggett, D (eds.).
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Soundings may also be taken to establish the ship's position as an aid in
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was instrumental in convincing the Royal Navy to adopt Massey's machine.
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devices particularly when navigating in shallower waters and on rivers.
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456:(Second ed.). Oxford, England: Oxford University Press. 1969.
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to make maps of the floor of a body of water, such as the
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No Sea Too Deep: The
History of Oceanographic Instruments
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National
Oceanic & Atmospheric Administration (NOAA)
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Pages displaying short descriptions of redirect targets
80:(metres) has become the standard for measuring depth.
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from this cry. The term lives on in today's world in
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431:National Oceanic and Atmospheric Administration
74:National Oceanic and Atmospheric Administration
579:The British Journal for the History of Science
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78:International System of Units
480:University of Michigan Press
88:"Sounding" derives from the
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180:of a ship, up against the
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539:Kemp, Peter, ed. (1993).
453:Oxford English Dictionary
327:Kelvin's sounding machine
131:, the technique of using
523:Hutton, Charles (1795).
503:Oxford University Press
107:, a geographical term.
702:(retrieved Sept 2006).
694:Depth sounding devices
493:Kemp, P., ed. (1976).
389:Multibeam echosounding
367:and patented in 1928.
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625:McConnell, A (1982).
406:Challenger expedition
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696:at Wikimedia Commons
365:Herbert Grove Dorsey
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223:'s 1066 landing in
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436:2012-07-07
413:References
400:Fishfinder
361:fathometer
295:Royal Navy
261:navigation
117:Mark Twain
55:bathymetry
274:anchoring
191:devices.
162:lead line
670:C&GS
612:40753266
604:25921680
371:See also
270:pilotage
201:medieval
125:pen name
43:sounding
245:leather
225:England
182:shrouds
170:plummet
168:with a
139:History
70:fathoms
18:Sounded
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309:. The
265:tallow
249:calico
178:chains
608:S2CID
586:(2).
574:(PDF)
253:serge
209:Bible
197:Roman
193:Greek
133:sonar
121:pilot
104:sound
98:sound
49:of a
47:depth
600:PMID
545:ISBN
319:buoy
272:and
213:Acts
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353:GPS
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