burst out downward, and probably there was no ice at all under the largest bubbles, which were a foot in diameter. I inferred that the infinite number of minute bubbles which I had first seen against the under surface of the ice were now frozen in likewise, and that each, in its degree, had operated like a burning glass on the ice beneath to melt and rot it. These are the little air-guns which contribute to make the ice crack and whoop.
At length the winter set in in good earnest, just as I had finished plastering, and the wind began to howl around the house as if it had not had permission to do so till then. Night after night the geese came lumbering in in the dark with a clangor and a whistling of wings, even after the ground was covered with snow, some to alight in Walden, and some flying low over the woods toward Fair Haven, bound for Mexico. Several times, when returning from the village at ten or eleven o'clock at night, I heard the tread of a flock of geese, or else ducks, on the dry leaves in the woods by a pond-hole behind my dwelling, where they had come up to feed, and the faint honk or quack of their leader as they hurried off. In 1845 Walden froze entirely over for the first time on the night of the 22d of December, Flints' and other shallower ponds and the river having been frozen ten days or more; in '46, the 16th; in '49, about the 31st; and in '50, about the 27th of December; in '52, the 5th of January; in '53, the 31st of December. The snow had already covered the ground since the 25th of November, and surrounded me suddenly with the scenery of winter. I withdrew yet farther into my shell, and endeavored to keep a bright fire both within
