FORMER BASINS IN THE CONNECTICUT VALLEY. H 



In nearly forty observations, upon heights varying from 260 to 5000 feet, the dif- 

 ference between the two instruments rarely exceeded twenty feet, and in only one 

 or two cases of great altitude, approached 100. Such an approximation to the 

 truth, surely the geologist must regard as of great value, especially as the observa- 

 tions can be made with so little inconvenience and delay. 



One of the most serious drawbacks upon this instrument, as appears to me, is 

 the difficulty of adjusting it, or of ascertaining its range. In either case several 

 observations must be made upon heights of several hundred feet. This is great 

 labor for every turn of a screw. My experience leads me to conclude that to 

 resort to the air-pump in such cases is not reliable. 



Former Basins in the Connecticut Valley. 



Originally, when the river stood at a higher level, this valley consisted of a suc- 

 cession of basins, or expansions in the stream, separated, or perhaps connected by 

 ridges, through which gorges were cut, and deepened by the river alone, or with the 

 aid of the ocean. At present, so deeply has the bed been worn down, that these 

 narrow lakes or ponds have disappeared. But they have left evidence of their 

 former existence by the terraces on their borders. The following ancient basins 

 are well marked. 



1. From the mouth of the river to Mid die town, a distance of twenty-five miles, it 

 is bounded by steep and rocky hills, with a narrow meadow occasionally. Where 

 the river enters this mountainous region, just below Middletown, the gorge is the 

 narrowest : but in its whole extent it has every appearance of having been formed 

 by the joint action of the river and the ocean. 



At Middletown the first, the longest, and the widest of these basins commences, 

 and extends to Mount Holyoke, in Hadley, a distance of fifty-three miles. On the 

 west side, however, the high land opens to the southwest of Hartford, so that on 

 the line of the Hartford and New Haven Railroad, the summit is only a few feet 

 above Connecticut river. It is certain, therefore, that when the river chose its 

 present bed through the rocky region below Middletown, that bed must have been 

 excavated nearly to its present depth ; otherwise the water would have chosen the 

 valley of the railroad in its way to the ocean. The passage through! the mountains 

 must have been lower than through Meriden, &c, to New Haven. 



At Enfield, in this basin, the river has cut through a sandstone range of con- 

 siderable height. The highest terraces, however, rise above the rocks in most 

 places ; yet, during the deposition of the lower terraces, the long basin above 

 described must here have been divided into two of nearly equal size. 



2. The second basin extends from Holyoke to Mettawampe (Toby,) in Sunder- 

 land, and Sugar-loaf, in Deerfield. From Holyoke, this basin must have extended 

 southerly along the west side of Mt. Tom, and the other almost continuous trap 

 ranges that extend to New Haven. Through this valley runs the canal railroad 

 from New Haven to Northampton. But nowhere is this valley more than one 

 hundred and thirty-four feet above the Connecticut at Northampton, and this is 

 not so high as some of the terraces. 



The second basin, also, extends northerly from Sunderland, on the west side of 



