[1. Gratacap, "The Ice Age," in "Popular Science Monthly," January, 1818, p. 321.] {p. 101} one of being _calcined in a many days passage through an immense furnace_."[1] Here we have a good deal more heat than is necessary to account for that vaporization of the seas of the globe which seems to have taken place during the Drift Age. But similar effects might be produced, in another way, even though the heat of the comet itself was inconsiderable. Suppose the comet, or a large part of it, to have fallen into the sun. The arrested motion would be converted into heat. The material would feed the combustion of the sun. Some have theorized that the sun is maintained by the fall of cometic matter into it. What would be the result? Mr. Proctor notes that in 1866 a star, in the constellation Northern Cross, suddenly shone with _eight hundred times its former luster_, afterward rapidly diminishing in luster. In 1876 a new star in the constellation Cygnus became visible, subsequently fading again so as to be only perceptible by means of a telescope; the luster of this star must have increased from five hundred to _many_ thousand times. Mr. Proctor claims that should our sun similarly increase in luster even one hundred-fold, the glowing heat would destroy all vegetable and animal life on earth. There is no difficulty in seeing our way to heat enough, if we concede that a comet really struck the earth or fell into the sun. The trouble is in the other direction--we would have too much heat. We shall see, hereafter, that there is evidence in our rocks that in two different ages of the world, millions of years before the Drift period, the whole surface of the [1. "The Heavens," p. 260.] {p. 102} earth was actually fused and melted, probably by cometic contact. This earth of ours is really a great powder-magazine there is enough inflammable and explosive material about it to blow it into shreds at any moment. Sir Charles Lyell quotes, approvingly, the thought of Pliny: "It is an amazement that our world, so full of combustible elements, stands a moment unexploded."