Association of American Geologists and Naturalists. 263 



ing respecting the origin of the supposed ancient currents, nor acqui- 

 esce in his views of an aUnost general submergence of the land at the 

 deposition of the drift, yet there is a value in his speculations respecting 

 especially the Gulf Stream, and a general consistency in the whole hy- 

 pothesis, which claim for his treatise a careful consideration. 



GEOLOGICAL DYNAMICS. 



Drift — Earthquake Theory — Elevation of Mountain Chains. — The 

 attention of this society has been zealously directed during the last three 

 years, to questions of geological dynamics. The phenomena and ori- 

 gin of our anticlinal axis, the nature of the forces concerned in the ele- 

 vation of mountain chains, and the cause, character and consequences 

 of earthquake motion, have been investigated by my brother. Prof. W- 

 B. Rogers and myself, but the subject which has enlisted the greatest 

 number of pens and called forth the most general discussion, has been 

 among the American geologists as among the European, the interesting 

 and complicated problem of the origin of the superficial bowlder stra- 

 tum, the great sheet of diluvium or drift. With the phenomena as they 

 exist in New England, a region where they are particularly striking, 

 we have been made familiar through the extended researches of Prof. 

 Hitchcock, Dr. C. T. Jackson and other geologists. At an early day, 

 1826, a clear account was given through the pages of the American 

 Journal of Science, by Mr. Peter Dobson of Connecticut, of the worn 

 and striated aspect of bowlders in that state, and very soon after this 

 Mr. Nathan Appleton of Boston, to whom this society is under large 

 obligations, first called attention to the universality of the smooothed 

 and grooved surfaces of the rocks wherever they had been protected 

 from atmospheric action. It is due to Prof. Hitchcock to state that early 

 in the history of the geological survey of Massachusetts, being guided 

 by his own observations, he investigated with much minuteness and care 

 the phenomena of smoothed and striated rocks and transported bowlders. 

 Profs. Mather, Emmons, Hall and Dewey, and Mr. Vanuxem, have des- 

 cribed the features connected with the drift of New York, and the for- 

 mer geologist embracing a wide survey has examined the phenomena 

 from New England to the Upper Lakes and to the sources of the Mis- 

 sissippi. In the western states the drift deposit has been described also 

 by Drake, Hildreth, Houghton, Lapham, Locke, Owen, Tappan and 

 others. 



Bearing upon the same general subject some interesting communica- 

 tions have been submitted to this Association, descriptive of icebergs and 



