Page:Walden, or, Life in the Woods.djvu/269

Rh shadiest and shallowest coves, some days or even weeks before the general freezing. The first ice is especially interesting and perfect, being hard, dark, and transparent, and affords the best opportunity that ever offers for examining the bottom where it is shallow; for you can lie at your length on ice only an inch thick, like a skater insect on the surface of the water, and study the bottom at your leisure, only two or three inches distant, like a picture behind a glass, and the water is necessarily always smooth then. There are many furrows in the sand where some creature has travelled about and doubled on its tracks; and, for wrecks, it is strewn with the cases of cadis worms made of minute grains of white quartz. Perhaps these have creased it, for you find some of their cases in the furrows, though they are deep and broad for them to make. But the ice itself is the object of most interest, though you must improve the earliest opportunity to study it. If you examine it closely the morning after it freezes, you find that the greater part of the bubbles, which at first appeared to be within it, are against its under surface, and that more are continually rising from the bottom; while the ice is as yet comparatively solid and dark, that is, you see the water through it. These bubbles are from an eightieth to an eighth of an inch in diameter, very clear and beautiful, and you see your face reflected in them through the ice. There may be thirty or forty of them to a square inch. There are also already within the ice narrow oblong perpendicular bubbles about half an inch long, sharp cones with the apex upward; or oftener, if the ice is quite fresh, minute spherical bubbles one directly above another, like a string of beads. But these within the ice are not so numerous nor obvious as those