The water in them freezes, and as it increases in bulk, the pipes burst.
Why are some springs never frozen?
Because water, much above the freezing-point, is always flowing into them from the earth, and thus they are kept too warm to freeze.
Why are some other springs frozen?
Because the water flowing into them comes from near the surface of the earth, and is soon made cold enough to freeze.
Does salt water freeze at the same temperature as fresh water?
No; fresh water freezes at thirty-two degrees, but salt water requires a lower temperature depending upon the amount of salt it contains.
How is this useful?
The surface of the ocean is never frozen over except in very cold latitudes; hence, vessels may sail on it at all seasons of the year, and carry the products of one country to another; thus adding much to our comfort and our enjoyment.
