Page:Polar Exploration - Bruce - 1911.djvu/58



almost any time during even a summer cruise, when there is a perfect calm and when the sun is low during the night, there may be found under the shadow of loose pieces of ice, which gently rest upon a glassy sea, newly-formed fine ice spicules floating on the surface: these ice spicules are dissipated when the rays of the sun play once more on the surface of the water. If the temperature of the water be taken at such a time it will be found to be about 29° F., which is therefore clearly about the temperature at which the polar seas begin to freeze. That is to say, about 3° F., below the freezing-point of fresh water, which, as the reader will know, freezes at 32° F.

Now, if the temperature of the air falls considerably below 28° F., say to 15° F., these ice spicules or crystals increase very rapidly, and the whole surface of the sea becomes covered with a considerable layer of them, which is known by polar seamen as "Bay ice." If there is a snow shower the snow mixes with