About three miles from the shore, and just visible from it, lay a small islet. It is not exactly correct to say islet. It was but a shoal of rocks--a small patch, apparently about a square pole in dimensions, and rising only a few inches above the surface of the water. This, too, only when the tide was out, for at all other times it was quite covered with the waves; and then there could only be seen a slender staff sticking up out of the water to the height of a few feet, and at the head of this appeared a sort of knob, or lump. Of course the staff had been placed there to point out the shoal in times of high tide, so that the sloops and other small vessels that traded up the bay might not run upon it by mistake, and so get wrecked. Only when the tide was low, then, was this little islet to be observed from the shore. Usually, it appeared of a jet black colour; but there were other times when it was as white as if covered a foot deep with snow, and then it showed plainer and more attractive. I knew very well what caused this singular metamorphosis in its colour. I knew that the white mantle that covered it was neither more nor less than a vast flock of beautiful sea-fowl, that had settled upon the rocks, either to rest themselves after so much flying, or to search for such small fish or Crustacea as might be left there by the tide. Now this little spot had long been to me a place of first-rate interest, partly on account of its remote and isolated situation; but more, I fancy, on account of these very birds, for in no other part of the bay had I seen so many of them together. It seemed also to be a favourite place with them; for at the going out of every tide, I observed them gather from all directions, hover around the staff, and then settle down upon the black rocks around it, until the latter were hidden from the view behind the white bodies of the birds. These birds were gulls; but there appeared to be several kinds of them; large ones and small ones, and at different times I had noticed birds of other kinds, such as the great terns and grebes, preening themselves in the same neighbourhood. Of course, from the shore the view one could have of these creatures was a very distant one, and it was difficult to tell to what species they belonged. The largest of them appeared not much bigger than sparrows, and had they not been on the wing, or so many of them together, they might have moved about unnoticed by any one passing along the shore.