In spring the sun not only exerts an influence through the increased temperature of the air and earth, but its heat passes through ice a foot or more thick, and is reflected from the bottom in shallow water, and so also warms the water and melts the under side of the ice, at the same time that it is melting it more directly above, making it uneven, and causing the air bubbles which it contains to extend themselves upward and downward until it is completely honeycombed, and at last disappears suddenly in a single spring rain. Ice has its grain as well as wood, and when a cake begins to rot or “comb,” that is, assume the appearance of honeycomb, whatever may be its position, the air cells are at right angles with what was the water surface. Where there is a rock or a log rising near to the surface the ice over it is much thinner, and is frequently quite dissolved by this reflected heat; and I have been told that in the experiment at Cambridge to freeze water in a shallow wooden pond, though the cold air circulated underneath, and so had access to both sides, the reflection of the sun from the bottom more than counterbalanced this advantage.