Suddenly your adversary’s checker disappears beneath the board, and the problem is to place yours nearest to where his will appear again.  Sometimes he would come up unexpectedly on the opposite side of me, having apparently passed directly under the boat.  So long-winded was he and so unweariable, that when he had swam farthest he would immediately plunge again, nevertheless; and then no wit could divine where in the deep pond, beneath the smooth surface, he might be speeding his way like a fish, for he had time and ability to visit the bottom of the pond in its deepest part.  It is said that loons have been caught in the New York lakes eighty feet beneath the surface, with hooks set for trout,—­though Walden is deeper than that.  How surprised must the fishes be to see this ungainly visitor from another sphere speeding his way amid their schools!

Yet he appeared to know his course as surely under water as on the surface, and swam much faster there.  Once or twice I saw a ripple where he approached the surface, just put his head out to reconnoitre, and instantly dived again.  I found that it was as well for me to rest on my oars and wait his reappearing as to endeavor to calculate where he would rise; for again and again, when I was straining my eyes over the surface one way, I would suddenly be startled by his unearthly laugh behind me.  But why, after displaying so much cunning, did he invariably betray himself the moment he came up by that loud laugh?  Did not his white breast enough betray him?

He was indeed a silly loon, I thought.  I could commonly hear the plash of the water when he came up, and so also detected him.  But after an hour he seemed as fresh as ever, dived as willingly and swam yet farther than at first.  It was surprising to see how serenely he sailed off with unruffled breast when he came to the surface, doing all the work with his webbed feet beneath.  His usual note was this demoniac laughter, yet somewhat like that of a waterfowl; but occasionally when he had balked me most successfully and come up a long way off, he uttered a long-drawn unearthly howl, probably more like that of a wolf than any bird; as when a beast puts his muzzle to the ground and deliberately howls.  This was his looning,—­perhaps the wildest sound that is ever heard here, making the woods ring far and wide.  I concluded that he laughed in derision of my efforts, confident of his own resources.

Though the sky was by this time overcast, the pond was so smooth that I could see where he broke the surface when I did not hear him.  His white breast, the stillness of the air, and the smoothness of the water were all against him.  At length, having come up fifty rods off, he uttered one of those prolonged howls, as if calling on the god of loons to aid him, and immediately there came a wind from the east and rippled the surface, and filled the whole air with misty rain, and I was impressed as if it were the prayer of the loon answered, and his god was angry with me; and so I left him disappearing far away on the tumultuous surface.