13/32 This is precisely what might have been expected; for it is a well established physical property of fresh water, that it attains its maximum density at the above-indicated temperature. In other words, a mass of fresh water at the temperature of 4 deg.Cent.has a greater weight under a given volume (that is, a cubic unit of it is heavier at this temperature) than it is at any temperature either higher or lower. Hence, when the ice-cold water of the snow-fed streams of spring and summer reaches the Lake, it naturally tends to sink as soon as its temperature rises to 4 deg. Cent.; and, conversely, when winter sets in, as soon as the summer-heated surface water is cooled to 4 deg., it tends to sink. |