The pond was my well ready dug. For four months in the year its water is as cold as it is pure at all times; and I think that it is then as good as any, if not the best, in the town. In the winter, all water which is exposed to the air is colder than springs and wells which are protected from it. The temperature of the pond water which had stood in the room where I sat from five o’clock in the afternoon till noon the next day, the sixth of March, 1846, the thermometer having been up to 65° or 70° some of the time, owing partly to the sun on the roof, was 42°, or one degree colder than the water of one of the coldest wells in the village just drawn. The temperature of the Boiling Spring the same day was 45°, or the warmest of any water tried, though it is the coldest that I know of in summer, when, beside, shallow and stagnant surface water is not mingled with it. Moreover, in summer, Walden never becomes so warm as most water which is exposed to the sun, on account of its depth. In the warmest weather I usually placed a pailful in my cellar, where it became cool in the night, and remained so during the day; though I also resorted to a spring in the neighborhood. It was as good when a week old as the day it was dipped, and had no taste of the pump.