PRESIDENT’S ADDRESS. 669 
East Atlantic Basin. Some of the shoreward slopes round the 
isolated oceanic islands must be still steeper—for instance, the 
Bermudas and the solitary Island of St. Thomas in mid-Atlantic, 
rise high above the surface of the sea, while at no great distance 
we find that the depth of the ocean is 17,000 feet. 
2. The next great feature of the ocean-bed is the existence of 
extensive submarine plains rising almost to the middle depth 
reached by the terrigenous deposits, but separated from them by 
deep, wide channels, and often having great basins or circumscribed 
depressions like submarine lakes on their surface. Occasionally 
these plains show evidence of having been caused by the subsi- 
dence of formerly existing land surfaces, but as a rule, the nature of 
the material of the sea bottom on these plateaux indicate only such 
deposits that settle from the ocean water far from land. They are, 
however, often traversed by steep ridges like submarine mountain 
chains, the peaks of which sometimes reaching almost to or above 
the sea level as oceanic islands, but in such cases the rocks are 
almost, without exception, of igneous origin and coral formations 
which indicate the influence of volcanic activity. The Pacific 
Archipelago presents a wonderful development of this character 
of the ocean bed. In every part of the sea bottom the deposit 
contains fragments of volcanic rock, especially pumice-stone, but 
these have been mostly derived from the slow sinking of particles 
that have fallen on the surface of the sea and been waterlogged 
while drifting along far from where they were dropped into the 
sea or washed out by the rivers from the land. 
3. The great channels which form the deeper but not the most 
profound parts of the ocean floor. They lie between the land 
and the submarine plains, at an average depth of 35 miles. They 
form a continuous reticulation all over the ocean bottom. If the 
ocean were gradually dried up until the shoreward shelf and the 
oceanic plains were exposed, the outline of the remaining ocean 
would somewhat resemble the form of the canals that have been 
observed to reticulate the surface of the planet Mars. 
4. Further evaporation of the sea would disclose the existence 
of profound and abrupt depressions—termed ‘“ deeps” in the floor 
of the most profound parts of the ocean bed. Probably only a 
few of them have been discovered by the sounding-wire, but they 
present remarkable features. They are generally in close vicinity 
to greatly elevated land, or to land on which intense volcanic and 
seismic or earthquake activity is prevalent. The most remarkable 
of the great depressions is the Tuscarora Deep, parallel with the 
east coast of Japan; the Kriimmel Deep, parallel with the west 
coast of South America ; the Ross Deep, in the Antarctic regions ; 
and the Penguin Deep, east of Kermadec Island, north-east of 
New Zealand, where the deepest sounding ever found was lately 
taken by H.M.S. “ Penguin.” 
