As for the inlet or outlet of Walden, I have not discovered any but rain and snow and evaporation, though perhaps, with a thermometer and a line, such places may be found, for where the water flows into the pond it will probably be coldest in summer and warmest in winter. When the ice-men were at work here in '46-7, the cakes sent to the shore were one day rejected by those who were stacking them up there, not being thick enough to lie side by side with the rest; and the cutters thus discovered that the ice over a small space was two or three inches thinner than elsewhere, which made them think that there was an inlet there. They also showed me in another place what they thought was a "leach-hole," through which the pond leaked out under a hill into a neighboring meadow, pushing me out on a cake of ice to see it. It was a small cavity under ten feet of water; but I think that I can warrant the pond not to need soldering till they find a worse leak than that. One has suggested, that if such a "leach-hole" should be found, its connection with the meadow, if any existed, might be proved by conveying some colored powder or sawdust to the mouth of the hole, and then putting a strainer over the spring in the meadow, which would catch some of the particles carried through by the current.
While I was surveying, the ice, which was sixteen inches thick, undulated under a slight wind like water. It is well known that a level cannot be used on ice. At one rod from the shore its greatest fluctuation, when observed by means of a level on land directed toward a graduated staff on the ice, was three quarters of an inch, though the ice appeared firmly attached to the shore. It was probably greater in the middle. Who knows but if our instruments were delicate enough we might detect an undulation in the crust of the earth? When two legs of my level were on the shore and the third on the ice, and the sights were directed over the latter, a rise or fall of the ice of an almost infinitesimal amount made a difference of several feet on a tree across the pond. When I began to cut holes for sounding there were three or four inches of water on the ice under a deep snow which had sunk it thus far; but the water began immediately to run into these holes, and continued to run for two days in deep streams, which wore away the ice on every side, and contributed essentially, if not mainly, to dry the surface of the pond; for, as the water ran in, it raised and floated the ice. This was somewhat like cutting a hole in the bottom of a ship to let the water out. When such holes freeze, and a rain succeeds, and finally a new freezing forms a fresh smooth ice over all, it is beautifully mottled internally by dark figures, shaped somewhat like a spider's web, what you may call ice rosettes, produced by the channels worn by the water flowing from all sides to a centre. Sometimes, also, when the ice was covered with shallow puddles, I saw a double shadow of myself, one standing on the head of the other, one on the ice, the other on the trees or hillside.
While yet it is cold January, and snow and ice are thick and solid, the prudent landlord comes from the village to get ice to cool his summer drink; impressively, even pathetically, wise, to foresee the heat and thirst of July now in January—wearing a thick coat and mittens! when so many things are not provided for. It may be that he lays up no treasures in this world which will cool his summer drink in the next. He cuts and saws the solid pond, unroofs the house of fishes, and carts off their very element and air, held fast by chains and stakes like corded wood, through the favoring winter air, to wintry cellars, to underlie the summer there. It looks like solidified azure, as, far off, it is drawn through the streets. These ice-cutters are a merry race, full of jest and sport, and when I went among them they were wont to invite me to saw pit-fashion with them, I standing underneath.
In the winter of '46-7 there came a hundred men of Hyperborean extraction swoop down on to our pond one morning, with many carloads of ungainly-looking farming tools—sleds, plows, drill-barrows, turf-knives, spades, saws, rakes, and each man was armed with a double-pointed pike-staff, such as is not described in the New-England Farmer or the Cultivator. I did not know whether they had come to sow a crop of winter rye, or some other kind of grain recently introduced from Iceland. As I saw no manure, I judged that they meant to skim the land, as I had done, thinking the soil was deep and had lain fallow long enough. They said that a gentleman farmer, who was behind the scenes, wanted to double his money, which, as I understood, amounted to half a million already; but in order to cover each one of his dollars with another, he took off the only coat, ay, the skin itself, of Walden Pond in the midst of a hard winter. They went to work at once, plowing, barrowing, rolling, furrowing, in admirable order, as if they were bent on making this a model farm; but when I was looking sharp to see what kind of seed they dropped into the furrow, a gang of fellows by my side suddenly began to hook up the virgin mould itself, with a peculiar jerk, clean down to the sand, or rather the water—for it was a very springy soil—indeed all the terra firma there was—and haul it away on sleds, and then I guessed that they must be cutting peat in a bog. So they came and went every day, with a peculiar shriek from the locomotive, from and to some point of the polar regions, as it seemed to me, like a flock of arctic snow-birds. But sometimes Squaw Walden had her revenge, and a hired man, walking behind his team, slipped through a crack in the ground down toward Tartarus, and he who was so brave before suddenly became but the ninth part of a man, almost gave up his animal heat, and was glad to take refuge in my house, and acknowledged that there was some virtue in a stove; or sometimes the frozen soil took a piece of steel out of a plowshare, or a plow got set in the furrow and had to be cut out.
To speak literally, a hundred Irishmen, with Yankee overseers, came from Cambridge every day to get out the ice. They divided it into cakes by methods too well known to require description, and these, being sledded to the shore, were rapidly hauled off on to an ice platform, and raised by grappling irons and block and tackle, worked by horses, on to a stack, as surely as so many barrels of flour, and there placed evenly side by side, and row upon row, as if they formed the solid base of an obelisk designed to pierce the clouds. They told me that in a good day they could get out a thousand tons, which was the yield of about one acre. Deep ruts and "cradle-holes" were worn in the ice, as on terra firma, by the passage of the sleds over the same track, and the horses invariably ate their oats out of cakes of ice hollowed out like buckets. They stacked up the cakes thus in the open air in a pile thirty-five feet high on one side and six or seven rods square, putting hay between the outside layers to exclude the air; for when the wind, though never so cold, finds a passage through, it will wear large cavities, leaving slight supports or studs only here and there, and finally topple it down. At first it looked like a vast blue fort or Valhalla; but when they began to tuck the coarse meadow hay into the crevices, and this became covered with rime and icicles, it looked like a venerable moss-grown and hoary ruin, built of azure-tinted marble, the abode of Winter, that old man we see in the almanac—his shanty, as if he had a design to estivate with us. They calculated that not twenty-five per cent of this would reach its destination, and that two or three per cent would be wasted in the cars. However, a still greater part of this heap had a different destiny from what was intended; for, either because the ice was found not to keep so well as was expected, containing more air than usual, or for some other reason, it never got to market. This heap, made in the winter of '46-7 and estimated to contain ten thousand tons, was finally covered with hay and boards; and though it was unroofed the following July, and a part of it carried off, the rest remaining exposed to the sun, it stood over that summer and the next winter, and was not quite melted till September, 1848. Thus the pond recovered the greater part.