"What would be the pressure of the water on a submarine at that depth?" asked Alfred.
"Pressure is calculated on the square inch of surface; for every twenty-eight inches the pressure is equal to one pound. If, therefore, 200 is multiplied by 12 and then divided by 28, the quotient will represent the number of pounds on each square inch," answered the captain.
"Why multiply 200 by twelve?" asked Ralph.
"Because there are twelve inches in a foot," said the captain.
"Oh, yes; I didn't happen to think of it; well, 200 by 12,—that's 2,400, and divided by 28, is——"
"Eighty-five," interrupted Alfred. "Well, that's not very much."
"Quite true," rejoined the captain; "but how many square inches are there in a square foot?"
"One hundred and forty-four," replied Alfred.
"Then, eighty-five times one hundred and forty-four makes quite a sum," continued the captain.
"Whew,——" said Ralph with a half whistle in his tone, "why, if I have made it out right, it's over 12,000 pounds. No wonder it isn't safe to stay down very long, if at all, at that depth."