80 J. D. Dana on the origin of some of the 



widely spread over the New Haven region, and tliey may have come 

 from Vermont or New Hampshire, where such rocks occur,* 



5. Rapidity of deposition. — The wasting of the glacier, beginning 

 as the warm Champlain era opened, (p. 06) would at first have been 

 slow, and mainly above. But after a while, the glacier would 

 have been reduced to a comparatively thin sheet of ice, and then, 

 through the heat conveyed into it in all directions by means of waters 

 from above, and that received through flowing waters and air below, 

 the rotting of the mass would have become general, and the unload- 

 ing of the glacier would have gone rapidly forward. The period of 

 years occupied by the deposition of the sand and boulders may there- 

 fore have been short. It may be queried, considering how much ap- 

 pears to have been done by a single wave, whether one year, or even 

 less, would not have sufficed for the upper division, or the upper 

 twenty feet, in the part of the formation rej^resented in figure 1, on 

 page 73. 



With so quick a way of dumping the load of the great glacier it is 

 nothing incredible that the channel of West Creek should have been 

 cut ofi^" from its northern continuation, the Beaver Pond basin ; nor 

 is it impossible that, by like means. Mill River should have had its 

 course through the same basin and channel intercepted by half a mile 

 of sand and gravel, and have been forced to open a new way for it- 

 self by Whitneyville, although deemed improbable for the reasons 

 stated on page 55. Even the floods of Niagara were thus stopped 

 short; the old gorge, as long since made known, was filled to the 

 brim for miles by the drift, and the river was turned ofi" to work out 

 another passage through the rocks.f The accumulations of a " ter- 



* Besides the boulders described on page 68, there are the following in more remote 

 localities. One, of trap, 6 miles in an air-line north of the city, 1-J- m. west of Ives' 

 Station, fifty rods west of W. Fenn's, south and east of a bend in the road, is 88 feet 

 in girt and 17 feet high, and must weigh over 600 tons. Less than half a mile south 

 of tliis spot, near, and east of, the " West "Woods " road, a little south of R. Warner's 

 house, there are four great trap boulders, nearly in a north-and-soutli line, the largest 

 50 feet in circuit. Half a mile north of the Mt. Carmel gap, a short distance west of 

 the raOroad track, (and in full sight from the cars when passing), there is a boulder of trap, 

 somewhat house-like in shape, which is 25 feet long by 14 wide and 16 high, with a 

 girt of 68 feet; and along side lies a slice from its broad face, averaging 4 feet in 

 thickness, which when a part of the mass, would have-made its diameters 25, 18 and 16 

 feet, and its original weight at least 450 tons. It shows traces of vertical lamination, 

 like a trap dike, and was probably taken off from some trap-mountain before it had fall- 

 en from its place. 



f Dr. Newberry in his memoir on Surface Geology, already referred to (p. 49), men- 

 tions the Ohio river as another that was diverted by the filling up of the old channel 



