Page:Winter - from the Journal of Henry D. Thoreau.djvu/74

60 15°—at 8 at our door. I went to the river immediately after sunrise; could see a little greenness in the ice, and also a little rose color from the snow, but far less than before sunset. Do both these phenomena then require a gross atmosphere? Apparently the ice is greenest when the sun is twenty or thirty minutes above the horizon.

From [a] smooth open place a great deal of vapor was rising, to the height of a dozen feet or more, as from a boiling kettle. This, then, is a phenomenon of quite cold weather. I did not notice it yesterday These open places are a sort of breathing holes of the river. Just as cold weather reveals the breath of a man, still greater cold reveals the breath of, i. e., warm, moist air over the river. When I went to walk it was about 10° above zero, and when I returned 1°+. I did not notice any vapor rising from the open places as I did in the morning when it was 16°— and also when it was 6°—. When the air is, say 4° or 5° below zero, the water being 32°+, then there is a visible evaporation. Is there the same difference, or some 40° between the heat of the human breath and that of the air in which the moisture in the breath becomes visible in vapor. This has to do with the dew point.—Next, what makes the water of those open places thus warm? and is it