A. 1st—Because the mass of water is so great that it requires a very long time to cool the whole volume down to 42 degrees:
2ndly—The ebb and flow of the sea interfere with the cooling influence of the air: and
3rdly—Salt never freezes till the surface is cooled down at least 25 degrees below the freezing point.
Q. Why do some lakes rarely if ever freeze?
A. 1st—Because they are very deep:
2ndly—Because their water is supplied by springs, which bubble from the bottom.
Q. Why does the depth of the water retard its freezing?
A. As the whole volume of water must be reduced to 42 degrees before the surface will freeze, the deeper the water, the longer it will be before the whole volume is thus reduced.
Q. Why do springs at the bottom of a lake prevent its freezing?