The Ocean Bottom Al 
of landsmen have come to regard seafarers as habitual exag- 
gerators or liars, so that they immediately discount any men- 
tion of a sea serpent. This public feeling of skepticism even 
prevents sailors from speaking about their experiences with 
unusual happenings at sea. 
Who knows but that there may still be species in the ocean 
deeps that have successfully eluded all our hooks, nets and 
trawls? 
Apart from these speculations about the ocean bottom, 
there is a definite body of scientific knowledge. It is con- 
cerned mainly with the mapping of the ocean bottom and the 
nature of the material of which it is composed. The scientific 
study of the form of the ocean floor is called submarine to- 
pography. 
LAND BENEATH THE SEA 
Regions of the ocean floor are classified according to depth. 
Along the shores of the world’s continents there are relatively 
shallow regions whose depths reach about 100 fathoms. 
These regions are really extensions of the continental land 
masses that happen to be submerged by the ocean. They are 
called continental shelves and in some places extend for long 
distances beneath the surface of the ocean. Siberia and 
Alaska are connected by a broad belt of submerged land no- 
where deeper than 100 fathoms. This belt conceivably may 
be the land, then above water, over which some scientists be- 
lieve men first came to the North American continent—the 
forefathers of the American Indian. The eastern coasts of 
North America have extensive continental shelves which pro- 
vide fine fishing banks. The British Isles are connected with 
the European mainland by a continental shelf. Such connec- 
