HAS THE DEEP OCEAN EVER BEEN LAND ? 409 
why should we only find tertiary sedimentary rocks on them? 
But if the islands were not then in existence the cause which 
has produced them could not have been acting in those localities, 
that is, they were not then oceanicareas. If these islands formed 
part of an upheaval of the ocean bed, then Mr. Darwin’s argu- 
ment would have been valid. But: this is not the case, the 
islands are merely huge heaps of lava and ashes, volcanic ejec- 
tions which have been erupted through the ocean bed, and bring 
up none of the older rocks with them. 
The shape of the bottom of the oceanic areas is also used as 
an argument in favour of the permanence of continents. It has 
been found that around the continents, the sea bottom sinks 
very gradually, for a variable distance from the coast, until it 
reaches a depth of ahundred fathoms or so; it then falls more 
suddenly, and ultimately becomes flat. Now, if this argument, 
which is advanced by Dr. Carpenter, means anything it means 
that the continental areas have never been elevated more than 
600 feet or so above their present level: for the sudden slope 
beyond the hundred fathom line is supposed to be part of the 
original continental upheaval, which has been planed down by 
denudation as far as that line and no further when the land stood 
some 500 or 600 feet higher than at present. But we know 
that oscillations in the level of the continental. areas, to a far 
greater extent than this, have often taken place, and it is absurd 
to suppose that all the great land masses have, at some time or 
other, been elevated 600 feet and no more above their present 
position. I suspect that the statement with regard to the 
hundred fathom line does not rest upon sufficient evidence ; but, 
if it is true, we must find some other explanation of it than the 
one offered by Dr. Carpenter. The more rapid fall of the 
bottom at a comparatively short distance from the coast may, 
perhaps, be accounted for by the more rapid deposition that 
takes place round the coast. We see the same thing in the fan 
formed by a river entering a lake, and on a coast line we have a 
series of fans running into each other. Tolerable permanence 
of level for a certain time would ensure the formation of a bank 
of deposit around the land. 
Dr. Carpenter also says that there are “no known submerged 
continental platforms in mid-ocean.”* He allows that there are 
raised plateaux in the middle of the Atlantic and in the middle 
of the Pacific, but he calls these “ upward bulgings of the median 
portions of depressed ocean floors.” He does not, however, ex- 
plain the difference between an upward bulging of an ocean 
floor and a submerged continental platform, and it is not easy to 
see how one can be distinguished from the other. Mr. Wallace 
says that the plateau of the Mid-Atlantic “is no doubt due to 
volcanic upheaval and the accumulation of volcanic ejections ;’+ 
* The Deep Sea and its Contents, Azmeteenth Century, April 1880, 
f Island Life, p, 98. 
