This submarine mine, however, in addition to the burst and heave of torn and upflung falling waters and foam, had a visible heart, a great, shining, wet, torpedo-shaped body, which rose on end beneath the stricken bird, and fell again with a splintering crash that shot up the heads of the diving birds half a mile away.  It might have been a thresher-shark, or some other northern shark, or it might have been a dolphin, which is bad, or a killer whale, which is a good deal worse, if it had not been a great gray seal seeking dinner; and its effect on the luckless skua was the effect of a battering ram, and the skua that fell back again with the fall of snarling water was to all intents and purposes a corpse.

But it was a good thing that he was so.  Had it been otherwise, had he tried to get away or fluttered, there would have been no more of him.  That is to say, the head of the seal came up—­or its wet and suggestive big nose did—­and poked about, trying to find the bird.  It had evidently meant to grab him, to engulf him utterly and forever in the first rush; but something—­some unlooked-for lift of a wave or turn of the bird—­had made the shot miss, or nearly miss, so that the bird had been hit by the bloated six-footer’s nose, instead of being crushed in its teeth—­its terrible long and glistening array of murderous teeth.

All the same, the nose blow was bad enough.  It was like being hit by the beak of a torpedo at full speed, fit almost to bash a boat in.

The seal was quite evidently looking for the bird, and, equally quite evidently, seemed bound to find him.  To know why it did not at once see him is to know that the seal’s view, from below the surface, of the world above is about a twelve-foot circle of white-gold light, that is all; and the skua, floating limp and floppy, had been, by chance, till then always carried hither and yon by the waves just outside that circle.  But that chance could not last.

Then came the other seal.  Came she easily and gracefully, as a seal should in her element, effortlessly gliding along, her head from time to time up like a dog’s—­some gentle dog’s, say a mild-eyed spaniel’s—­looking about.  She was just a female seal.  She knew nothing of the bird or her companion, who were at sea-level, and more often than not hidden in the trough, till she came sliding down the slope of a round-barreled swell, practically on top of them.  Then it was too late to avoid mutual recognition.

Quick as sound she had seen, had realized, had spun on her apology for a tail, and had gone, leaving a little trail of foam behind her to prove her speed and her coyness.  But, quick as light, the magnificent male seal had sunk from sight, leaving a little chain of bursting bubbles behind to mark his speed.  And the last that was seen of that lady seal was a speck far on the horizon, going like a masterless torpedo, alternately leaping forward through the air and shooting along on, or just under, the surface—­switchbacking, they call it; and that, I dare to fancy, if it proves anything, proves that the coyness was only make-believe, and that she had allowed the daring admirer to catch her up and force her to act as if she were already vanquished and using the last arts of swift swimming she knew.