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The Great Islands Under The Sea

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Author Topic: The Great Islands Under The Sea  (Read 2337 times)
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« on: April 30, 2007, 12:13:28 pm »

THE GREAT ISLANDS UNDER THE SEA                                                                         continued

The first extensive soundings of the Atlantic were made by warships of the British,
American, German and French Fleets in the latter half of the 19th century, using
basically the same means of establishing depth as those used since ancient times.

Throughout history, captains of vessels were more interested in how shallow, rather
than how deep, the waters were, in order to prevent their ships from striking rocks on
the sea bottom or being grounded on shoals. 

Until sonar was invented, depth was established by hurling loaded weights with
measured lines, and later wire, off the bow of a ship under sail and then, when the
ship caught up with the throw and line was vertical, hauling it up to measure.  This
was repeated at intervals.  If a vessel was stationary, a long line could be lowered
to the bottom to establish and approximate depth.  The composition of the bottom
was ascertained by coating the underside of the lead weight with wax or grease, so
that when it made contact with material on the bottom, it would stick to it and indi-
cate that the bottom was composed of sand, mud, marl, shell, or other material.

The accuracy of the measurements was limited, however, by the weather and the
state of the sea at the time of the soundings.

Such age-tested methods, while successful for shorelines because of the frequency
of the soundings, could give only an incomplete picture of the bottom of the open sea,
although an improved lead-line method was still employed with the first naval research
expeditions of the 19th century in the Central Atlantic, preparatory to the laying of the
transatlantic cables.

« Last Edit: April 30, 2007, 12:37:33 pm by Bianca2001 » Report Spam   Logged

Your mind understands what you have been taught; your heart what is true.

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