Q. Why is the water at the bottom of a river never frozen?
A. Because when water is colder than 42 degrees, it instantly ascends to the surface; and (if it freezes) floats there till it is melted.
(When a river is frozen, the water below the surface is never less than 42°.)
Q. Show the wisdom of God in this wonderful exception to a general law.
A. If ice were heavier than water, it would sink; and a river would soon become a solid block of ice, which could never be dissolved.
Q. Why does not the cold ice on the surface of a river chill the water beneath, and make it freeze?
A. 1st—Water is a very bad conductor, and is heated or chilled by convection only:
2ndly—If the ice on the surface were to communicate its coldness to the water beneath, the water beneath must communicate its heat to the ice, and the ice would instantly melt: and
3rdly—The ice on the surface acts as a shield to prevent the cold air from penetrating the river to freeze it below the mere crust.