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



Milford turnpike, the removal of the soil in several places has ex- 

 posed large surfaces that were planed and grooved by the glacier ; 

 and there is no doubt that but for the covering of earth the rocks in 

 all directions would be found glacier-marked. 



The stones, or boulders, in the foot of the glacier, that were scratch- 

 ed and polished while doing this work of abrasion, are often to be 

 found where the drift of the hills has been freshly uncovered. One of 

 four tons weight lies on the roadside along the Milford turnpike, a 

 few rods above Allingtown ; and many others of smaller size have 

 been thrown out at the recent excavation for the Derby railroad, near 

 the toll-gate on the same road. 



By the means mentioned an immense amount of rock material was 

 taken aboard the glacier for transportation southward ; and yet there 

 were no lateral moraines in the ordinary sense of this expression. 

 The surface of the Connecticut valley glacier was white and spotless. 

 From the Green Mountain ridge to the White Mountains of New 

 Hampshire there was not a projecting peak to afford a grain of dust. 



The special effects of the glacier over the New Haven region inclu- 

 ded the making {ci) of hills, and {b) of valleys or excavations. 



First — Its Excavations. — The excavations would naturally have 

 been most extensive where there was no trap or other hard rock in 

 the way to prevent deep ploughing. The valleys of the Quinnipiac 

 and West River beyond doubt date their origin long back of the Gla- 

 cial era, from the time the trap and sandstone ridges which bound 

 them were first thrown u]3 above the level of the sea ; but still they must 

 have been scoured out by the moving ice, and have had their depth 

 and width much increased. Whether the work of the ice or not 

 is uncertain ; yet it is a fact that the whole western side of the West 

 river valley is stripped clean of the sandstone which once existed 

 there, and which was a part of the formation that originally stretched 

 across to the top of the West Rock ridge ; not a square yard of 

 sandstone is left in place over the metamorphic rocks of its western 

 slope. The close shaving of the sandstone on the east side of East 

 Rock, and its still more complete removal on the west side, have been 

 already alluded to as probably part of the effects of the glacier. Be- 

 sides the excavations in these valleys, others very extensive must 

 have been made over the whole central part of the New Haven region, 

 from its southern limits to the mountains on its northern border in 

 Hamden ; for this was the great central valley of the region. 



Among the depressions over this region, the most remarkable is that 

 of the Beaver Pond Meadoios [bm., in tlie map). It is a large marshy 

 area sunk 20 feet below the general surface, lying in the center of the 



