In that brilliant flight of scientific fancy, the _Time Machine_, Mr. H.G. Wells has pictured the closing years of the earth in some such long-drawn agony as this. He has given us a vision of a desolate beach by a salt and almost motionless sea. Foul monsters of crab-like form crawl slowly about, beneath a huge hull of sun, red and fixed in the sky. The rocks around are partly coated with an intensely green vegetation, like the lichen in caves, or the plants which grow in a perpetual twilight. And the air is now of an exceeding thinness. He dips still further into the future, and thus predicts the final form of life:-- "I saw again the moving thing upon the shoal--there was no mistake now that it was a moving thing--against the red water of the sea. It was a round thing, the size of a football perhaps, or it may be bigger, and tentacles trailed down from it; it seemed black against the weltering blood-red water, and it was hopping fitfully about." What a description of the "Heir of all the Ages!" To picture the end of our world as the result of a cataclysm of some kind, is, on the other hand, a form of speculation as intensely dramatic as that with which we have just been dealing is unutterably sad. It is not so many years ago, for instance, that men feared a sudden catastrophe from the possible collision of a comet with our earth. The unreasoning terror with which the ancients were wont to regard these mysterious visitants to our skies had, indeed, been replaced by an apprehension of quite another kind. For instance, as we have seen, the announcement in 1832 that Biela's Comet, then visible, would cut through the orbit of the earth on a certain date threw many persons into a veritable panic. They did not stop to find out the real facts of the case, namely, that, at the time mentioned, the earth would be nearly a month's journey from the point indicated! It is, indeed, very difficult to say what form of damage the earth would suffer from such a collision. In 1861 it passed, as we have seen, through the tail of the comet without any noticeable result. But the head of a comet, on the other hand, may, for aught we know, contain within it elements of peril for us. A collision with this part might, for instance, result in a violent bombardment of meteors. But these meteors could not be bodies of any great size, for the masses of comets are so very minute that one can hardly suppose them to contain any large or dense constituent portions.