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PROCEEDINGS OF THE AMERICAN ACADEMY 



The elevation of the lake above the Pacific has been taken from the 

 surveys of the railroad engineers, obtained while laying the line from 

 Arequipa to Puno. Professor James Orton inclines to the opinion 

 that the whole basin of Lake Titicaca, with the high plateau to the 

 westward, is gradually sinking, because the successive observations 

 made from early times give a gradually diminishing height. Thus 

 far, the few measurements taken can hardly be more than a chance 

 coincidence, when we remember the uncertainty and great divergence 

 attending all measurements of heights taken to within a comiiaratively 

 very recent period. Tlie experience of the topographers of the late 

 geological surveys in the Rocky jNIountains has been very similar ; and 

 yet we are hardly prepared for such a sweeping generalization as 

 the sinking of the greater part of the Rocky Mountains from much 



