Physical geography. By Mary Somerville ...

CHAP. XIII. SOUNDINGS IN THE ATLANTIC. 137
never be subverted by any physical cause: a general inundation from
the mere instability of the ocean is therefore impossible.
[On the 15th of November 1849, in latitude 31~ 59' north, longitude 58~ 43' west, Lieut. J. C. Walsh, U.S. Navy, (under the
instructions of Lieut. M. F. Maury, Superintendent of the National
Observatory at Washington), sounded with 5700 fathoms of wire
without reaching the bottom. The inference from this experiment
is that the depth of the ocean exceeds, at that place, 34,200 feet, or
more than six statute miles.
Commander Barron, on board the U. S. Ship John Adams, reports,
in May 1851, deep sea soundings made while crossing the Atlantic.
They are as follows:North West
Date. Latitude. Longitude. Fathoms. Feet.
May 3.,.......33 50..........520 34/.......2,500 = 15,000
9......... 32 06/.........44o 47......... 5,500 - 33,000 got bottom
10.........31~ 01..........44~ 31.........2,300 13,800 got bottom
17.........Peak of Pico in sight...........670 = 4,020 got bottom
21.........35~ 07/........25o 43/........1,040 - 6,240 got bottom
These soundings indicate that the great basin which holds the
waters of the Atlantic Ocean, has a surface broken into irregular
depressions and elevations analogous to the deep valleys and cloudcapped mountains of the dry land. The persevering efforts of Lieut.
Maury to ascertain the laws which regulate the motions of the sea
and of the air will result in adding largely to the knowledge of
many phenomena which have hitherto been deemed mysteries,and
eluded the satisfactory investigation of physicists. And amongst
the inquiries not the least interesting are those relating to the depth
of the ocean, and the form of its bottom.']
CHAPTER XIII.
The Continent of Australia-Tasmania, or Van Diemen's Land-Islands —
Continental Islands -Pelasgic Islands —New Zealand-New Guinea --
Borneo-Atolls - Encircling Reefs - Coral Reefs-Barrier Keefs -Volcanic Islands —Areas of Subsidence and Elevation in the Bed of the
Pacific-Active Volcanoes- Earthquakes-Secular Changes in the Level
of the Land.
THE continent of Australia, situate in the Eastern Pacific Ocean
is so destitute of large navigable rivers that probably no very high
[' See Maury's Explanations and Sailing Directions to accompany the
Wind and Current Charts. Washington, 1851.]
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