A. Because they keep continually sending forth fresh water, which prevents the lake from being reduced to the necessary degree of coldness.
Q. Why is it colder in a thaw than in a frost?
A. When frozen water is thawed, it absorbs heat from the air and objects around to melt its ice, in consequence of which the cold is greatly increased.
Q. Why is it warmer in a frost than in a thaw?
A. When water freezes it gives out its latent heat, in order that it may be converted into solid ice; and as much heat is liberated from the water into the air, we feel warmer.
Q. Why does salt dissolve ice?
A. Water freezes at 32°, but salt and water will not freeze till the air is 25° colder: if, therefore, salt be added to frozen water it becomes liquid, unless the thermometer stands below 7°, (which it never does in our island).
Q. Will any thing do instead of salt?
A. Yes; any acid, such as sulphuric, nitric, &c.