698 GEOLOGY OF OLD HAMPSHIRE COUNTY, MASS. 



above tlie sea. The tat lavers are one-fourth to one-half inch thick and 6 

 inches apart. This great height was clue to the rajjicl advance of the Millers 

 River delta across the channel farther south, which checked the current 

 to the north. How rapid this was is seen by the section, fig. 41 (p. 688), 

 where far out in the delta the sands rest directly uj^on the rock. As the 

 delta was extended westward its sands were doubtless carried up gradu- 

 ally over the clays, for in the long erosion scarp cut in the western face 

 of this delta from Turners Falls around nearly to ^Montague village, only a 

 small thickness of sand rests upon the clays, which rise to a height of about 

 213 feet above the sea and rest upon till or sandstone with a thickness of 

 aboiTt 34 feet. The laj^ers average about 1 inch, one-half fat clay, two- 

 thirds tine sand. (See tig. 35, p. 629.) 



CLAYS IN THE HADLEY LAKE. 



I have mentioned an isolated occurrence of clay poorly exposed at a 

 schoolhouse in the north of Greenfield. Around Greenfield A'illage the 

 clavs are in great force and rest upon till, as seen at the clay pit in the 

 village and on Fall River where the road to Franklin Park crosses it. 

 These clays were continuous through the notch of the Deei-field River, and 

 perhaps also coimect farther north, through the passage at the mouth of 

 Fall River, with the Turners Falls clays. Southward they crop out 

 abundantlv around the erosion basin of the Deei-field River, to near its 

 south end, opposite the mouth of the river gorge, where, from the increased 

 current and the increased material brought in 1)\' the river, the clays are 

 replaced by a great thickness of sand, which, in the center of the basin, 

 becomes exceedingly fine, with distant clayey partings, as seen in the 

 Wapping cutting (PI. XVIII; p. 694), where these fine sands rest discord- 

 antly on the problematical reddish sands which are there described. 



Farther south, through Deerfield and Hatfield, the sand ])lains are 

 nowhere cut through to the clays below until the region of complex 

 oxbows of the Connecticut Avest of Hatfield village, described later (p. 734), 

 is reached, where, in the terrace scarj^, the clays appear in great force; only 

 at one place, at a clay pit near the pistol factory, is the substratum — here 

 coarse till — exposed. 



Southward, beyond the infl-uence of the Deei-field, the Avhole l)road bot- 

 tom of the lake is underlain by a continuous stratum of clay of imknown, 



