The Ocean Bottom 25 
straight down. (One nautical mile is only slightly greater 
than 1000 fathoms, 1013.7 to be exact.) The chart will also 
show such interesting features as the Atlantic Ridge which 
extends down the middle of the Atlantic Ocean; the water 
here is much shallower than in the surrounding regions. The 
Azores, St. Paul Rocks, Ascension Island, and Tristan da 
Cunha are all parts of the ridge which extend above the sur- 
face. Another interesting ridge is the Telegraph Plateau, ex- 
tending from England to Newfoundland, the resting place of 
several transoceanic telegraph cables. 
HOW THE OCEAN BOTTOM LOOKS 
It is likely that not many readers have strolled about on 
the ocean floor, so that they may not be familiar with its ap- 
pearance. Such first hand experience is neither necessary nor 
possible at present (at least for the greatest depths) and so 
we must content ourselves with what we can find out about 
the bottom. by dredging, or employing deep sea snappers. 
The snappers are shaped like a clam shell with two cup-like 
halves. Upon touching the bottom a powerful spring snaps 
the jaws shut and a sample of the bottom is enclosed. 
Still another device for sampling the bottom is a coring 
tube. It is merely a hollow tube which is lowered until it hits 
the bottom in an upright position. A charge of explosive then 
drives it into the bottom, forcing a considerable length of the 
bottom up into the tube. The sample is then hauled aboard. 
When the tube is opened the bottom is in its actual form, 
layer by layer. With gadgets such as these the nature of the 
bottom is studied by oceanographers. For shallow water the 
tallow on the hand lead may be relied upon to bring up a 
small sample of the bottom. 
