Chapter 105 Spring - 1

The great digging of the ice-diggers usually makes the ice of a pond thaw sooner; for even in cold climates the waves of water, driven by the wind, eat away the ice around it.But this year, Walden was not affected by this, because it immediately put on a new thick layer of ice to replace the old one.This one pond never melted so early as those of the adjacent marshes, because it was much deeper, and had no flowing springs below to melt or wear away the ice above.I have never seen it burst in winter; except the winter of 1852-1853, which gave so severe a trial to many ponds.It usually freezes at the mouth of April, a week or ten days later than Flint Lake or Fair Harbor, starting from the north shore, and some shallow places, where it freezes first.It is more in season than any wave in the neighborhood, and indicates the absolute progress of the seasons, unaffected by the vagaries of temperature.A few days of severe cold in March would have delayed the opening of the other ponds, but the temperature at Walden increased almost without interruption.On March 6th, 1847, a thermometer plunged into the center of Walden Pond and read thirty-two degrees, or freezing point, and near the shore, thirty-three degrees; Two and a half degrees; in shallow water twelve rods offshore, under a foot of ice, thirty-six degrees.The difference of three and a half degrees in temperature between the shallow and deep waters of the latter lake, and the fact that this one is largely shallow, may account for its much earlier melting than Walden.At that time, the ice in the shallowest waters was several inches thinner than that in the center.In mid-winter, the center of the lake is the warmest, where the ice is thinnest.Similarly, anyone who has waded near the shore of a lake in summer knows that the water near the lake is much warmer, especially where there is only three or four inches of water. The depths are much warmer.In spring, the sunlight not only exerts its power on the sky and the earth, which is gradually warming, but its heat also penetrates the ice a foot or more thick, and in shallow water, it is reflected from the bottom to the top, warming the water waves. and melted the lower part of the ice, while from above the sun melted the ice more directly, made it uneven, raised air bubbles, rose and fell, until at last they were all honeycombed, and by the last spring rains, they All gone.Ice, like trees, has texture, and when a block of ice begins to melt, or honeycomb, no matter where it is, the air bubbles and the water surface are always connected at right angles.Where there is a projecting rock or log below the surface of the water, the ice on them is always much thinner, and is often dissolved by the reflected heat; Frozen ice in lakes and marshes, with cold air flowing below, can make the effect of both above and below, and the heat of the sun reflected from the bottom of the water can still outweigh this effect.When a warm rain in mid-winter melts the snowy ice of Walden Pond, leaving only a black, hard, transparent ice in the middle, there will be a decayed, but thicker self-ice. , about a rod or more wide, along the shore of the lake, is formed by this reflected heat.Also, as I have already said, the air bubbles in the ice rise up like convex lenses from below to dissolve the ice.

This phenomenon of the four seasons of the year changes daily on the lake, but on a small scale.Generally speaking, the shallow water warms more quickly than the deep water every morning, but not much warmer after all, and it also cools more rapidly every evening until morning.A day is a microcosm of a year.Night is winter, morning and evening are spring and autumn, noon is summer.The crackling and rumbling of the ice signaled the change in temperature.On the 24th of February, 1850, after a cold night, in the pleasant dawn, I ran to Flint Lake to pass the day, and was surprised to find that I had only broken the ice with an axe. , it was like hitting a gong, and the sound extended to several rods, or it could be said that I sounded a taut drum.About an hour after the sun rose, the lake felt the heat of the sun slanting down from the mountains, and began to rumble; It went on like this for three or four hours.Noon was the time for naps, but toward evening the sun withdrew its influence and the rumbling resumed.Every day in normal weather, the lake fired its evening salute, well timed.Only at noon there are too many cracks and the air is not elastic enough, so that it loses its resonance altogether, and fish and muskrats probably don't hear it and are stunned by the shock.Fishermen say that the "thunder of the lake" scares the fish away from their hooks.The lake doesn't thunder every night, and I don't know when to expect it, but, though I can't tell a difference from the weather, it does sometimes.Who would have thought that something so big, so cold, and so thick-skinned could be so sensitive?Yet it has its laws, and it thunders to obey it, as the bud should bud in spring.The earth, covered with warts, is full of life.The largest lakes are as sensitive to atmospheric changes as mercury in a tube.