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Page:Popular Science Monthly Volume 73.djvu/298

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POPULAR SCIENCE MONTHLY
 
PSM V73 D298 Upper rapids and the rock rim determining the water distribution of niagara falls.png

Fig. 2. View of Upper Rapids, at the head of which is the rock-rim determining the distribution of water, as it leaves the basin above (descent 55 feet). This rock-rim also determines the level of the Upper Lakes.