320 



SCIENCE. 



[Vol. II., No. 31. 



covered the Ohio river near the site of New Rich- 

 mond, a few miles above Cincinnati; and presented 

 the hypotliesis, that one effect of this invasion of the 

 Ohio valley by the glacial ice was to form an im- 

 mense dam of ice and morainic debris, which ef- 

 fectually closed the old channel way, and set back the 

 water of the Ohio and its tributaries, imtil, rising 

 to the level of the Licking Kiver divide, it prob- 

 ably found an outlet through Kentucky, around the 

 glacial dam. The writer of the essay, after review- 

 ing the evidence, regards Mr. Wright's hypotlie- 

 sis as proved beyond a reasonable doubt. He also 

 claimed, that during the period of the continuance 

 of the dam, the principal tributaries of the Ohio had 

 their valleys filled with sediment carried down and 

 dumped into them by the mountain torrents and 

 other streams which drained the area south from 

 the glaciated region; that subsequently, when the 

 barrier disappeared, the rivers recut their channels 

 through the silt deposits, probably by spasmodic low- 

 ering of the dam, in such a manner as to leave the 

 deposits in a series of more or less regular terraces, 

 which in favored localities subsequent erosion has 

 failed to obliterate, though from steep slopes it 

 has removed their every trace. The elevation of 

 this dam at Cincinnati, as determined from the upper 

 limit of the fifth Monongahela River terrace, would 

 be somewhere about 625 feet above low water there 

 in the present Ohio. 



In discussing this paper, Professor Lesley said 

 that there were two separate glacial formations to be 

 considered, and the two could not be correlated. 

 The ice-dam could not thus be explained. Professor 

 Wright had discussed the subject with clearness, 

 claiming that the dam was glacial; but at best there 

 were only a few places in the west where the height 

 of the ice could be measured. 



The eroding po-wer of ice. 



BY J. S. NEWBEBBT OF STEW YOKE. 



The object of this essay was to enter a protest 

 against the theories of certain geologists who claim 

 that glacial ice has not played an important part in 

 the erosion of valleys. They have undertaken to 

 deny that ice has any great excavating power. Ex- 

 amples of utterances of this school, the speaker said, 

 were to be found in Prof. J. D. Whitney's Climatic 

 changes; in papers by Prof. J. W. Spencer, on the 

 Old outlet of Lake Erie ; by Mr. W. M. Davis, on the 

 Classification of lake basins, and the erosive action 

 of ice; and remarks on the same subject by Prof. 

 J. P. Lesley. 



The most important heresies which had been ad- 

 vanced in regard to this subject were, first, the denial 

 that there was ever a glacial period; second, if there 

 was an ice period, it was a warm and not a cold one; 

 third, that the phenomena usually ascribed to glacial 

 action in the record of an ice period were generally 

 due to icebergs ; fourth, that ice has little or no erod- 

 ing power, and that glaciers have never been an im- 

 portant geological agent. Professor Newberry pro- 



ceeded, in controversion of these theories, to give the 

 results of his extended studies of geological action in 

 the Alps and in many different regions of the United 

 States and Canada. These observations lead to the 

 conclusions, 1°. That the glacial period was a reality, 

 and that its record constitutes one of the most impor- 

 tant and interesting chapters of geological history; 2°. 

 That this was a cold period; 3°. That ice has a great, 

 though unmeasured and perhaps immeasurable, erod- 

 ing power; and that, in regions whicli they have 

 occupied, glaciers have been always important, and 

 often preponderating, agents in effecting geological 

 changes. 



No cautious geologist would assert cr concede that 

 all lake-basins had been excavated by ice, but to deny 

 its influence in their formation would be a far greater 

 error. The basins of our great lakes, and of many of 

 our smaller ones, bear the traces of ice that has 

 moved in the line, at least approximately, of their 

 major axes. The broad, boat-shaped basins indicate 

 the work of this same agency. The islands of Lake 

 Erie are carved from the solid rock: their surfaces 

 and sides, and the channels between them, are all 

 glaciated. The plastic ice has inwrapped those 

 islands, fitting into every irregularity, and carving, 

 with the sand it carried, every surface. The marks 

 of glaciation are to be seen on mountain belts from 

 Canada to Mexico. Even at the present day glaciers 

 are transporting enormous loads. In midsummer the 

 Aar glacier brings down 280 tons per day; the Juste- 

 dal glacier of Norway wears down, it is estimated, 

 69,000 cubic meters of solid rock annually. These 

 measuriimenls of the eroding power of two small 

 glaciers should show the fallacy of a denial of the 

 excavating power of ice. Dr. Newberry concluded by 

 citing authorities on the subject. 



This paper elicited the most acrimonious discussion 

 of the meeting. Professor Lesley took exception to 

 certain phrases in the paper which seemed to cast a 

 reflection upon the methods of his coadjutors, — men 

 who were conscientiously engaged in scientific inves- 

 tigation, and had seen reason for breaking away from 

 the trammels of opinion formulated by Agassiz and 

 Ramsey. For himself, he did not believe in the theory 

 of erosive glacial processes, and he asserted that there 

 was no good reason for believing that the basins of 

 the great lakes were so produced. He claimed that 

 the basi^j of Ontario was a Silurian valley ; the basins 

 of Erie, Michigan, and Huron, were Devonian val- 

 leys. Ice had no more eroding effect than a piece of 

 sandpaper has upon a rough board. He believed in 

 the eroding of water, and represented his idea of the 

 relative power of ice and water, as follows: Ice, 1; 

 rain-water, 10; acidulated water, 100; ice set with 

 stones, 1,000; water set with stones, 10,000. 



Professor Newberry disclaimed any intention of 

 attacking the young men of science who were labor- 

 ing in this field. He re-affirmed the positions taken 

 in his paper. On the other hand. Professor T. Sterry 

 Hunt declared his substantial agreement with the 

 views of Professor Lesley. On account of the length 

 of this debate, the five-minute rule for discussions 

 was adopted and subsequently enforced. 



