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mountains and filled up the valleys. But in doing that a great 

 change was effected in it. They knew that, after walking in the 

 snow for some time, the bottom of their boots was covered, not 

 with snow, but with an icy mass. The pressure on their heels had 

 generally hardened a frozen lump there. They learned the 

 important fact that pressure could convert snow into ice. It was 

 so in the Alps. The vast superincumbent masses of snow pressed 

 that beneath it into the narrow valley, and so formed what was 

 called a glacier. It was somewhat diiEcult to describe a glacier, 

 but they might imagine a huge river winding among the hills, its 

 surface rugged with the vast waves which a stormy wind had raised 

 on it, and then imagine that, in a moment, the river was frozen. 

 The crests of the waves wei'e ridges of ice. The depressions 

 between them ran down for hundreds of feet. Such was the great 

 ice river called a glacier. Amongst researches of scientific men 

 during recent years, few had more interest than those of Agassiz, 

 Forbes, and recently Tyndall, on the subject of glaciers. To the 

 works of Pro. Tyndall on the " Forms of Water," from which he 

 had borrowed the title of his lecture, he would refer those wishing 

 to know what there was to be said on snow and ice. One would 

 scarcely think such a mass of rigid ice moved, but it had been 

 proved that it moved just as a river, faster in the middle than at the 

 sides, faster at the point towards which it bent than that from 

 which it turned. In fact, a glacier did evei'ything that a river did, 

 and they had often had melancholy proof of their movement. 

 Glaciers were the sources of rivers ; the Rhine, the Rhone, the 

 Oregon, and others had their sources in them. The hot summer 

 melted them as they came down into the narrow valleys. The 

 water trickled through the cracks, plunged into their crevasses in 

 hundreds of little cataracts, and at last found a vent at the bottom 

 of the valley. But the Alps were not the only mountains where 

 there were glaciers — the stupendous peaks of the Himalayas were 

 surrounded with them. In the midst of their inaccessible 

 peaks could be discerned the glittering of the great ice rivers. 

 How they dug out the valleys and polished the sides of the 

 mountains between which they moved. How they carried 

 down to their termination the huge boulders which had fallen 

 from the mountains upon their surface during their journey, 

 and, when they melted, left them stranded on the plains. The 

 hiUs and valleys of Scotland and Wales still bore marks 



