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[ti:Exploring the Sea-Floor]
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[00:00.93]Lesson 30
[00:02.38]Exploring the sea-floor
[00:09.48]How did people probably imagine the sea-floor before it was investigated?
[00:17.45]Our knowledge of the oceans a hundred years ago was confined to the two-dimensional shape of the sea surface
[00:24.90]and the hazards of navigation presented by the irregularities in depth of the shallow water close to the land.
[00:33.53]The open sea was deep and mysterious,
[00:36.86]and anyone who gave more than a passing thought to the bottom confines of the oceans probably assumed that the sea-bed was flat.
[00:45.67]Sir James Clark Ross had obtained a sounding of over 2, 400 fathoms in 1839,
[00:53.26]but it was not until 1869, when H.M.S. Porcupine was put at the disposal of the Royal Society for several cruises
[01:03.38]that a series of deep soundings was obtained in the Atlantic and the first samples were collected by dredging the bottom.
[01:11.84]Shortly after this the famous H.M.S. Challenger expedition established the study of the sea-floor
[01:19.01]as a subject worthy of the most qualified physicists and geologists.
[01:24.37]A burst of activity associated with the laying of submarine cables
[01:29.62]soon confirmed the Challenger's observation that many parts of the ocean were two to three miles deep,