MD - atmospheres of pressure

Yet not to speak of the peril of the thing, it is to be doubted whether this course is always the best; for it is but reasonable to presume, that the longer the stricken whale stays under water, the more he is exhausted. Because, owing to the enormous surface of him—in a full grown sperm whale something less than 2000 square feet—the pressure of the water is immense. We all know what an astonishing atmospheric weight we ourselves stand up under; even here, above-ground, in the air; how vast, then, the burden of a whale, bearing on his back a column of two hundred fathoms of ocean! It must at least equal the weight of fifty atmospheres. One whaleman has estimated it at the weight of twenty line-of-battle ships, with all their guns, and stores, and men on board.

- Ch. 81