Page:Popular Science Monthly Volume 85.djvu/83

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remains below the base of El Capitan, and which he believes dammed the downflowing waters and formed a lake six miles in length. Subsequently, sediments filled Lake Yosemite until they made the entrancingly beautiful meadows of to-day. A continuation of this process is now beheld in the outgrowing delta of Tenaya Creek which gradually is encroaching upon Mirror Lake.

Messrs. Matthes and Calkins of the Geological Survey have intimated to the writer that the forthcoming report of their latest reconnoissancereconnaissance [sic] will endeavor to prove that the Yosemite Valley was produced almost entirely by various forces of erosion as revealed by their investigation of the influence of corrasive forces upon the fissured zones of granite. They are now looking for such concrete evidence.

In this summary of the several theories of the genesis of the Yosemite, the general drift of their method of presentation has been to lead to a few conclusions based on concrete facts. But, perhaps, the first and most logical conclusion is that the evidence is still far from being complete. Local geologists, however, have much faith that some new discoveries are about to be made public by the government investigators. The absence of rock sills outcropping along the rim of the valley has been explained as being due to their overburden of detritus." And yet there are reasons for believing that the solid bottom of the Yosemite did actually subside during the period of upheavals and dislocations. The enigmatic formation of the domes suggests the expansion of plastic masses of igneous rocks. If these waves of stone once swelled to such stupendous heights, there must have been intervening troughs. And so, the original sinking away of the valley floor along the lines of cross-fracture still is obvious to many competent observers.