18 SURFACE GEOLOGY. 



through thick woods, I used barometers for getting their heights, except Nos. 11, 

 12, 13, and 14, which were obtained by levellings. Along this route the rock often 

 projects through the terraces, and shows decided evidence of powerful erosion by 

 aqueous agency, some hundreds of feet above the present stream. 



12. This section is in Whately, on the west bank of Connecticut river, and 

 extends only to the third terrace above the river. Had I followed up the side of 

 the mountain in the west part of the town, no doubt I should have found beaches, 

 and most likely one or two other terraces above No. 3. Indeed I know of one 

 terrace, say 100 feet higher than No. 3, about two miles south of the line followed 

 by No. 12, and I shall in the sequel point out a very high beach in the north part 

 of Whately. The principal uses of this section, thus imperfect, are to show that 

 the lowest terrace along the Connecticut is sometimes quite high (32 feet here), 

 and that the height of the broadest terrace in the Connecticut valley, which is No. 

 3, is less than it is nearer to the gorges; a fact which shows the influence of those 

 gorges in the accumulation of the materials of the terraces. 



As already stated, there are two branches to this second basin, one extending 

 north through Deerfield and Greenfield, and the other south through East Hamp- 

 ton, Westfield, Southwick, &c, nearly if not quite to Long Island Sound. These 

 branches are separated from Connecticut river by an almost continuous ridge of 

 trap and sandstone, as may be seen on the large accompanying map of the surface 

 geology of the Connecticut valley. This ridge is breached in Deerfield by Deerfield 

 river, in Westfield by Agawam river, and in Simsbury by Farmington river. On 

 the two first of these rivers are two remarkable sub-basins, sunk some 80 or 100 

 feet below the general level of the valley, and exhibiting on their margins fine 

 examples of terraces. As these cannot be well shown upon Plate III, I have 

 devoted separate ones, but on a larger scale, to their exhibition. (See Plates IV and 

 VII.) They both extend a considerable distance along the rivers, and show the 

 surface geology, especially the terraces and old river beds. 



The Deerfield Basin. 



13. Where Deerfield river emerges from its long Ohor, between Shelburne and 

 Conway, into the Connecticut valley, it has formed several terraces; a section of 

 which No. 13 exhibits; though on the south side of the river I have failed to 

 measure two small terraces. But on the north side of the stream a tongue of four 

 or five terraces has been thrown forward, perhaps a mile long, forming a ridge a. 

 little over a hundred feet high, with regular terraces on its south side. The stream 

 here descends rapidly, and so do the terraces slope in the same direction, although 

 I did not measure the rate of descent. It is so obvious to the eye that I thought 

 a measurement hardly necessary, especially as I find the same fact almost every- 

 where upon lateral terraces. They always have as great a slope as the stream on 

 which they occur, and sometimes greater. 



Until I discovered the tongue of terraces above described, I was of opinion that 

 the basin of Deerfield was once occupied by terrace materials to the height of No. 3 

 (yellow) on Map No. 1, Plate III, which is the usual level of the Connecticut valley 



