678 GEOLOGY OF OLD HAMPSHIEE COUNTY, MASS. 



to the left, and worked back north from the Ijrook to be mentioned to the 

 oldest till, giving two more sections, 2 i-ods farther from the center on either 

 side, and in the most diflficult part of the hne. (See PI. XV, and PI. XVIII, 

 figs. 2, 3, at p. 694.) 



POSITION AND CONTOUR OF THE TERRACE. 



Coming down from Deerfeld, the great plain of the Borden base line 

 (Ibt) sinks across Whately and Hatiield from 220 feet to 170 feet and 

 abuts upon "The Rocks," a low, jagged reef of exposed ledges, back of 

 and above which the lake bench flanks the higher hills to the west. At the 

 north line of Northampton this plain (1 b t) rises by a gradual slope to the 

 height of 203 feet, and still flanks the southern prolongation of the ridge for 

 nearly a mile soi;tli and merges around the south end of Elizabeth Rock 

 with the delta sands (1 s h) which fill the great Northampton Bay and rise 

 gradually to 295 feet in Florence. Resting thus on the west against the 

 rocks, the plain on the east overhangs the westernmost portion of the great 

 Hadley bend of the Connecticut, which has here eaten into and destroyed a 

 large portion of it. At its southern end, also, brooks have cut down into 

 the clays and obscured its connection with the delta sand farther south. 

 In all directions between north, east, and south the valley is open and 

 many miles wide. Mount Toby rises in the plain 3 J miles to the northeast, 

 and it is a point whence one gets a rare \'iew of the beaiitiful valley. The 

 plain lay thus in the open waters of the Hadley Lake, and it was formed 

 more than 100 feet below the surface of the lake waters. 



From the clay pit at the southeastern corner of the plain one goes down 

 the steep slope 70 feet to the river, at the extreme western point of the great 

 bend, over an iiubroken succession of laminated clays, which rise to within 

 6 feet of the surface, being capped by sand, and as I could trace them some 

 way north in the old cutting of the Connecticut River Railroad, to which 

 the new cutting runs nearly parallel, and found traces of the same clays at 

 the north end, I assumed the upward succession here to be rock, till, heavy 

 clays, and sand, and that this gave the greatest height of the clays for this 

 portion of the valley, and I had no conception of the exceedingly complex 

 anatomy of what seemed a very simple and normal section. 



