Crossing the Atlantic, we sighted a glittering white rock rising fifty feet out of the water.  It was, I found, the Island of Saint Paul's.  It had a curious appearance, standing thus alone in the ocean 500 miles from the coast of America, and 350 from the Island of Fernando Noronha-- the snowy pinnacle of a submarine mountain.  We hove-to close to it, and a boat being lowered, Mr McRitchie, Mr Brand, Jerry, and I, went on shore.  The whole rock is not three-quarters of a mile in circumference. Its white colour, we found, was produced by a thin coating of a substance formed by the washing off of the birds' dung, collected there in a succession of ages.  The rock was covered with birds--my old friends, the booby and the noddy, I had so often read about.  They stared at us with a stupid look as we pulled up, not at all able to make us out, and in no way disposed to make way for us.  Gerard and I were for knocking as many as we could on the head; but Cousin Silas would not allow us, observing that we did not want them for food, and that they had a far better right to the rock than we had.  The booby, Mr McRitchie told us, is a species of gannet, and the noddy a species of tern.  The first lays her eggs on the bare rock, but the latter constructs a nest with sea-weed.  While the doctor was eagerly hunting about for specimens of natural history, we were amused by watching the proceedings of some of the few inhabitants of the rock.  By the side of several of the noddies' nests we saw a dead flying-fish, evidently deposited there by the male bird.  Whenever we succeeded in driving away any one of the females, instantly a big crab, which seemed to have been watching his opportunity from the crevices of the rocks, would rush out, and with greedy claws carry off the prey.  One fellow, still more hungry, ran away with one of the young birds.  Another was going to make a similar attempt.