108 THE HAUNTS OF LIFE 
tively little is known of the vast zones between 
the end of the light’s reach and the floor of the 
sea, so that, although they are included in the 
idea of the Deep Sea, we may confine our- 
selves in this study to the floor of the great 
abysses. This is one of the largest haunts of 
life, occupying about roomillion square miles, 
?.e. more than a half of the whole earth’s sur- 
face; and it is the strangest. It is not difficult 
to get comparatively near it, within a stone’s- 
throw of it, for we can toss a pebble into it 
from the deck of a liner; but no one has ever 
seen it. It is a bourne from which no trav- 
eller can return. Yet we know a great deal 
about it, thanks to the patience of explorers. 
The world of the deep sea is very deep, for 
the average depth of the ocean is 2™% miles; 
and, as vast areas are comparatively shallow, 
there must be other parts extraordinarily 
deep. Just as the earth’s crust has been 
buckled into great mountains (the true moun- 
tains, not those that are formed by the unequal 
weathering of plateaux), so it is dimpled down 
into depressions. The very deep holes are 
called “ deeps”; and the so-called “ Challenger 
deep” in the North-West Pacific is nearly 6 
miles in depth, namely, 5269 fathoms. If one 
