18 BULLETIN OF THE 



raphy of the region and the author's idea of the direction and limits of 

 two trains. He noticed the angular shape of the blocks, recognizing the 

 consequent distinction between them and the rounded boulders buried 

 in the drift beneath, and considered that, from their position on the sur- 

 face of the drift, they must have been deposited later than that forma- 

 tion. He rejected both the view which attributed their distribution to 

 currents of water, and that which attributed it to icebergs, and came to 

 the final conclusion that the difficulties besetting every hypothesis of 

 their origin were so great, that no satisfactory explanation could be 

 given. 



It was in 1846, the year following that of the publication of Dr. 

 Hitchcock's paper, that Professors H. D. and W. B. Rogers set forth 

 their views in regard to the origin of these boulder trains. The agency 

 to which they were disposed to attribute the phenomena was the " par- 

 oxysmal or sudden and violent disturbance of the slightly flexible crust 

 of the earth, causing, in the period of the northern drift, a partial eleva- 

 tion and displacement of the bed of the great frozen sea, which occupies 

 the arctic latitudes, and sending its waters with all their ice in a sudden 

 inundation over all the northern lands of the two continents." The 

 Rogers brothers published at the same time a sketch map of the region, 

 which does not differ essentially from that published by Dr. Hitchcock. 



Sir Charles Lyell, in the " Antiquity of Man," describes two trains 

 composed of "green chloritic rock," which are identical with the two 

 mentioned by previous writers. He further states that there are five 

 other parallel trains composed of limestone blocks, and originating in 

 the Richmond Range, which lies to the east of the ridge in Canaan, and 

 which he supposes to be made up of limestone. These seven supposed 

 trains he exhibits upon a diagram, and represents the chloritic trains as 

 crossing the Richmond and Lenox Ranges through gaps between the 

 several peaks of those ranges. He expresses the belief that, at the time 

 of the drift period, the highest points of the Canaan, Richmond, and 

 Lenox Ranges formed chains of islands in an ocean, and that the gaps 

 in the Richmond and Lenox Ranges were straits, through which floated 

 icebergs bearing the chloritic blocks from the exposed parts of the 

 Canaan Range, and dropping them to their present positions. 



Rev. J. B. Perry, in both of his accounts of these boulders, speaks of 

 seven trains, two of chloritic slate, and five of limestone. The trains 

 originate, according to Mr. Perry, partly upon a range of hills in Canaan, 

 N. Y., but more especially upon the Richmond and Lenox Ranges, 

 where the five limestone trains can be traced to their exact sources upon 



