Topographical Features of the Xew Haven region. V9 



In contrast with the basin, the Quinnipiac valley near the village of 

 North Haven and north of it has its lower flats exceedingly narrow 

 and the uj^per plain of great extent ; and here, concordantly, the red 

 sandstone is but a little way beneath the surface, for it outcrops along 

 the river, and, as I am informed by Mr. D. H. Pierpont, is the bottom 

 of all wells in the village. But the poor condition of the terraces in 

 the Quinnipiac basin cannot be attributed solely to its extent and 

 depth ; it must be owing partly to the currents that swept through 

 the basin in the era of the melting glacier ; for the upper plain or ter- 

 race, evidently for the same cause, has in general been left remarka- 

 bly low, often not half its normal height, about North Haven and to 

 the north. It is to be noted also that the drift formation or plain 

 south of the basin may owe something of its extent and height to the 

 diminished velocity which the waters would have had after passing 

 East Rock, as they there escaped the bounds of the Quinnipiac val- 

 ley, and were free to spread widely to the westward. 



4. Origin of the material of the drift. — The sand, gravel and 

 stones of the drift-deposit of the plain came largely from the Red 

 sandstone formation; (1) the pulverized sandstone aflTording sand; 

 (2) the associated conglomerate yielding pebbles and stones ; (3) the 

 wear of fragments from the harder varieties of sandstone and con- 

 glomerate making other stones or pebbles. There are some pebbles 

 of trap, but they are very few in comparison with what the prece- 

 ding source supplied. The rest came from the region of crystalline 

 rocks to the northwest and northeast. 



The great trap boulders may have been derived from any of the 

 trap mountains to the north. Those of the western border of the New 

 Haven region, which are often tabular in form and sometimes thick- 

 laminated in structure, were probably carried off from the heights be- 

 tween the western of the Hanging Hills of Meriden and Mt. Tom, 

 though possibly in part from the West Rock ridge more to the south. 

 The great fallen masses in some of the valleys of the Meriden moun- 

 tains resemble many of these boulders in form, in fine-grained text- 

 ure, and in laminated or jointed structure. The masses of the Judges' 

 Cave are probably from these more northern trap ridges which, as 

 already mentioned, are the highest of the valley. This view of their 

 origin accords with the fact that the gneiss boulders so common along 

 with them are probably from the adjoining region of the town of 

 Granby, or from Massachusetts, farther north, as stated by Percival 

 after a comparison of the rocks. The quartz and quartzite boulders 

 may be from the adjoining region in Massachusetts. But they are 



