Instrumenting the sea floor

The oceanic abyss two to four miles below sea level is more forbidding than outer space. Nevertheless, experimentation is under way to explore and exploit this region, using both unmanned instruments and manned vehicles Although more than 70 per cent of the earth's crust is beneath the oceans, this portion of the earth is little known and scarcely used. Man has throughly explored most of the land areas of the earth — sometimes with great difficulty and at great risk — and has sailed for centuries on the surface of the oceans, but has yet to learn very much about that land directly beneath the keel of his ship.