10 
THE OCEAN WORLD. 
importance of making and recording deep sea soundings is 
established by the successful immersion of the transatlantic 
telegraph. 
At the bottom of the Atlantic there exists a remark- 
able plateau, extending from Cape Eace in Newfoundland, 
to Cape Clear in Ireland, a distance of over two thousand 
miles, with a breadth of four hundred and seventy miles : 
its mean depth along the whole route is estimated at two 
miles to two miles and a half. It is upon this telegraphic 
plateau, as it has been called, that the attempt was made 
to lay down the cable in 1858, and it is on it that the 
enterprise has been so successfully completed, during the 
year 1866. The surface of this plateau had been pre- 
viously explored by means of Brooke’s apparatus, and the 
bottom was found to be composed chiefly of microscopic 
calcareous shells (For am inif era), and a few siliceous shells 
(IHafmnaceiv). These delicate and fragile shells, which 
seemed to strew the bottom of the sea, in beds of great 
thickness, were brought up by the sounding-rod in a state 
of perfect preservation, which proves that the w r ater is re- 
markably quiet in these depths, — an inference which is 
fully borne out by the condition in which the cable of 
1858 was found, when picked up in 1866. 
The first exploration of this plateau was undertaken by 
the American brig Dolphin, which took a hundred sound- 
ings one hundred miles from the coast of Scotland, after- 
wards taking the direction of the Azores, to the north of 
which bottom was found, consisting of chalk and yellow 
sand, at nine thousand six hundred feet. To the south of 
Newfoundland, the depth was found to be sixteen thousand 
five hundred feet. In 1856, Lieutenant Berryman, of the 
American steamer Arctic, completed a line of soundings 
from St. John, Newfoundland, to Yalentia, off the Irish 
coast, and in 1857, Lieutenant Dayman, of the English 
steamship Cyclops, repeated the same operation : this last 
line of soundings, the result of which is represented in the 
accompanying section, differed slightly from that followed 
by Lieutenant Berryman. 
Fig. 3. Section of the Atlantic Telegraph. 
