_From Norton's "Elements of Geology." By permission of Ginn and Company_ ONE PEBBLE IN ITS TIME PLAYS MANY PARTS Here are pebbles faceted in different ways by glaciers. No. 1 has six facets. No. 4, originally a rounded river pebble, has been rubbed down to one flat face. Nos. 3 and 5 are battered little travellers faceted on one side only. Notice how No. 5 got his face scratched just as I did. ] [Illustration: PEBBLE FACETED BY WIND-BLOWN SAND You remember how the glaciers ground flat faces or facets on the pebbles, don't you? Here is another example of Nature's lapidary work, but here she has used wind and sand instead of ice. ] V. A Greater Cæsar and His Commentaries Well, there he is again, you see, Mr. Glacier of the Ice Age. He's always turning up, everywhere you go in earth history. As Shakespere's Mr. Cassius said of Mr. Julius Cæsar, "he bestrode the world." And, like the Roman Cæsar, this Cæsar wrote the story of his own exploits; but although a vastly greater conqueror than the famous Roman, he was even more modest. Cæsar and his Commentaries, our High School friend will tell you, nearly always refers to himself in the third person; but in his commentaries on his travels and exploits the Old Man of the Mountain didn't even use his own name. He left the editors of his manuscript to find out who he was. HOW THE GREAT LAKES WERE TIPPED UP One of the most striking things he did, of which he wrote the record on the walls, was to tip up the Great Lakes. You remember just how he made them. Well, it seems that as he started back home he tipped them up. Suppose you could pick up the vast stone bowls that hold these lakes and tip them toward the north as easily as you can tip a bowl of water, what would the water do? It would fall lower along the south shores of the lakes and rise along the northern shores, wouldn't it? Then suppose the lakes were kept tipped up in this way for ages, and summer wind storms and winter tempests dashed waves against their shores, what would happen? Stone walls rising above the shore would have terraces cut into them, and the line of these terraces would tilt toward the north. There are terraces just like that on rocks bordering the Great Lakes, and the explanation of their tilt is that the lakes themselves were tipped up, and that the Old Man of the Mountain did the tipping. The rock crust of the round earth bends under great weight like an arch. So when the enormous weight of the glaciers of the Ice Age was on a portion of the arch it bent down. Then, as the glaciers retreated, the weight of them was shifted northward all the time. Finally when the glaciers in the region of the lakes had melted quite away the arch slowly rose into place again and lifted the terraces above the water line as we see them to-day. Throughout regions the glaciers visited you find rocks polished like mirrors; in other cases they are scratched, and in others deeply grooved.