April 3, 1876.] -^4:,) [Price. 



formation, and long antecedent in deposition. But tliere is no reason why 

 the paste should not be formed through all time, where there are mountain 

 glaciers, grinding the rocks of the descending defiles, with a water under- 

 flow, frosts and rains, to spread it over the lower country, to an indefinite 

 extent through indefinite time. 



There certainlj^ seems to be no warrant for the supposition of a polar 

 ice-sheet over South America, while a cause for the phenomena seen seems 

 much nearer. There are the Cordilleras, ever ice-covered, with valleys 

 filled with glaciers grinding upon the rocks, and n.aking paste or Till of 

 their comminuted materials, and incessant freezings and thawings and 

 rains to carry down the product over the mrface of the land, now as well 

 as when the first drift deposit was made. Further information is certainly 

 wanted upon this subject, and it may be hoped that Professor Orton, now 

 about to visit the Amazon, may afford it. Mr. Kerr, in his Report on the 

 Survey of North Carolina, in 1875, makes observations pertinent and in- 

 teresting : "Till or initial drift," which "may be seen everywhere on the 

 hills and slopes of the Piedmont region, and less conspicuously, even in 

 the eastern territory of the Quarternary proper." p. 157. "Evidently 

 these materials" (the gold gravels) "have descended the slopes of the moun- 

 tains and ridges, at whose bases, or on whose lower and gentle inclines 

 they are found. By what force ? Certainly not of water. Neither are 

 they moraines ; accumulations at the foot of descending ice masses. They 

 are simply beds of till, which have crept down the declivities of the hills and 

 mountains, exactly as glp-ciers descend the Alpine valley, by successive 

 freezing and thawing of the whole water-saturated mass, both the expansion 

 of freezing and granitation contributing to the downward movement; and 

 with each thawing and advance, the embedded stones and gold particles 

 dropping a little neare the bottom." p. 156. This idea may explain much 

 of the appearances that perplex geologists, without driving them to the 

 theory of an immense polar ice-sheet glaciation. All past time, since the 

 mountains rose from the sea, gives room for normal causes to complete their 

 work, with the results we witness ; and account for Till being found upon 

 the surface as well as beneath the drift, and that without a polar ice-sheet. 



Those who concur in the conclusion that there have been continental 

 ice-sheets of great thickness, and destructive of all life where they moved, 

 are not agreed as to their cause, source, or extent. Agassiz insists that their 

 cause is cosmic, and more than the normal glaciers of high mountains; and 

 he and James CroU, and Winchell, and others, give them a polar center 

 and a flow towards the tropics down to at least the 39th degree of latitude, 

 and Agassiz extends them into the tropics. James Geikie, with Croll, as- 

 cribes to them an astronomical cause, but makes the mountains of Norway 

 and Sweden the source and center of the ice-distribution. Winchell infers 

 a mountain at the North Pole adequate to the production and movement 

 hither of the great ice-sheet. This want of accord among these eminent 

 glacialists is an argument of considerable force to show that the theory is 

 without a tenable foundation, 



PKOC. AMER. PniLOS. SOC. XVI. 97. 3f 



