"It was while these features were taking form in the depths of the range, the particles of the rocks marching to their appointed places in the dark, that the particles of icy vapor in the sky, marching to the same music, assembled to bring them to the light. Then, after their grand task was done, these bands of snow flowers, the mighty glaciers, were melted and removed, as if of no more importance than dew destined to last but an hour."[7] [Footnote 7: "The Mountains of California." John Muir.] [Illustration] HIDE AND SEEK IN THE LIBRARY How do you suppose warm water--of all things!--could have caused the Ice Age? This theory is one that was offered by a very eminent geologist, Doctor Shaler, of Harvard.[8] [Footnote 8: "Nature and Man in America."] In the same book he also explains how the old men of the mountain may have helped to make New York City, although they were never there in their lives, of course. When you take up geology as a special study--I hope you will--you will find that there were five particularly heavy snowfalls during the long winter. But why not look it up now? If you can't do it just get somebody else in the family to do it for you. Where is father's college geology? In the last two of these storms Mr. Labrador rode all over New England and clear to the sea, where he amused himself for a long time by setting icebergs drifting out over the Atlantic. How do they know about the icebergs? That's one of the interesting things the books tell. These books also show how Niagara Falls acts as a great time-clock that tells how long ago it was since the glaciers visited us. According to the record on the "dial" it was somewhere between 20,000 and 30,000 years ago. (Of course this isn't what _we_ would call very close timekeeping; but remember, in the long story of the earth even a hundred thousand years is a mere tick of the clock.) And the way this clock is running down shows we're going to lose Niagara Falls in the course of time. All falls finally run down in the same way. This is the rather flippant way my high school friend put it: "First, the water falls over the waterfall; then the waterfall falls, piece by piece, and the water falls no more. It's a sad case." (You'll see what he meant, quickly enough, when you read up on waterfalls. Your geography tells, doesn't it? Well, then, of course _you_ know.) But here's a question you can answer right out of this chapter. Which one of the illustrations shows that the mammoths and the cave men lived on earth at the same time? That the mammoth was seen in the flesh by those remarkable artists of the caves is plain, but what do you say to seeing a mammoth in the flesh in these days? Remember the mammoths have all been dead for thousands of years. (_Elephant_, _Mammoth_, _Siberia_.) What is there about the climate of Siberia that made this strange thing possible?