The Atlantic is also relatively deeper and less cumbered with islands than the Pacific, which has the higher ridges near its shores, constituting what some visitors to the Pacific coast of America have not inaptly called the "back of the world," while the wider slopes face the narrower ocean, into which for this reason the greater part of the drainage of the land is poured...

a) What has at first determined the position and form of the Atlantic ocean?
b) What changes has it experienced in the lapse of geological time?
c) What relations have these changes borne to the development of life on the land and in the water?
d) What is its probable future?