Let us admit that the pressure of the atmosphere is represented by the weight of a column of water thirty-two feet high.

In reality the column of water would be shorter, as we are speaking of sea water, the density of which is greater than that of fresh water.

Very well, when you dive, Ned, as many times 32 feet of water as there are above you, so many times does your body bear a pressure equal to that of the atmosphere, that is to say, 15 lb.

for each square inch of its surface.

It follows, then, that at 320 feet this pressure equals that of 10 atmospheres, of 100 atmospheres at 3,200 feet, and of 1,000 atmospheres at 32,000 feet, that is, about 6 miles; which is equivalent to saying that if you could attain this depth in the ocean, each square three-eighths of an inch of the surface of your body would bear a pressure of 5,600 lb.