MUSEUM OF COMPARATIVE ZOOLOGY. 



259. 



in a general sense, applying to the whole formation, and is then not 

 closely limited to its lithologioal meaning. Bearings are all magnetic. 

 Fage references to previous writings are made in parentheses after the 

 author's name ; the titles are given in the list above. 



A. Turner's Falls, Mass, (figs. 32, 33, 34). — This manufacturing 

 town is on a corner of land on the left bank of the Connecticut, which 

 here makes a considerable detour from its usual course, and on the way 

 exposes an excellent continuous section of sandstones and trap for more 

 than a mile. This is best examined by beginning on the northwestern 

 bank, one eighth of a mile below the lower suspension bridge (A, fig. 32), 

 where the back of the main trap range is clearly seen. This range has 

 its beginning on the southwest flank of Mount Toby in Sunderland, in 

 a layer of trap making an inconspicuous ridge; Hitchcock has de- 

 scribed its upper contact with sandstone in a brook a mile and a half 

 southeast of Sunderland. It then advances northwest, and ascends on 

 the back of Dccrfield Mountain, gaining the summit a few miles before 

 the Deerfield Elver outs through the ridge to the Connecticut; two 

 railroads pass through this gorge and cut the trap, but do not, so far as 

 I could see in passing, show any contacts. East of Greenfield the Poet's 

 Seat is the culminating point ; here the ridge is doubled, with a shallow 

 valley along its top, probably indicating a bed of sandstone or tufa, or a 

 strike fault. It is the upper surface of this main trap sheet that comes 

 to the river's edge below Turner's Falls (A, fig. 32); and going up 

 stream the Ijright red shaly sandstone is soon met lying upon its vesic- 

 ular, amygdaloidal surface, quite conformable to its slight irregularities, 

 and showing no signs of local baking at the junction, or of any branch- 

 ing intrusions from the trap below. The sandstone strikes N. 66° E., 

 dips 35° S. E. throughout the section. Following up the bank, we pasa 

 obliquely across the strike of the sandstone, and just before coming to 

 the bridge reach the first posterior trap (B). The contact is unfortu- 

 nately hidden here ; it might be found by searching on the face of this 

 posterior ridge farther northeast. The trap is at first dense, but a little 

 beyond the bridge becomes vesicular, and so continues up to the en- 

 trance of Fall River. Looking southwest across the river, one may see 

 an outcrop of rocks about in line with the strike of this trap, but they 

 seem to be bedded ; no ridge is visible in that direction, and I believe 

 the trap ends about where the river crosses it. Going up stream the 

 trap is seen continuously except in two places where covered by sand- 

 stone : the first is in a little hollow on its back (C), about one third of 

 the way to the mouth of Fall Kiver, where the bedding of the sandstone 



