110 BULLETIN OF THE 



Locality 13. Section numbers, 175-182 b. Farmington River Gap, Tariffville. Per- 

 cival's Report, pp. 391, 393. Percivai's notation, A. to E. IV. 2 (2). 



The main and anterior ridges are traversed by the Farmington River 

 at TariflFville (Fig. 8) ; the Connecticut Western Railroad passes through 

 the gap and exposes the complex structure and the upper surface of 

 the anterior ridge in a long cut a quarter of a mile east of the vil- 

 lage. The upper surface is seen again on the east bank of the river, 

 just above the road bridge.-^ 



A double sheet, as if of two flows. Lower sheet generally dense ; 

 sub-amygdaloidal, very porphyritic and glassy toward upper surface ; 

 upper portion very vesicular, and near surface contains " spike " amyg- 

 dules. No local close grain in trap at top of sheet; sand grains 

 conformably stratified in vesicles and small irregularities of surface ; 

 mixture of large and small fragments of trap with sand over surface, 

 this mixture passing laterally into a tufa bed ; trap fragments often 

 rounded as if water-worn. 



Upper sheet compact at the base ; sub-amygdaloidal and vesicular 

 in upper portion ; generally very porphyritic and originally possessing 

 a glassy base ; overlying sandstone not seen in railroad cut, but well 

 shown on opposite river bank below, locality 13', where it carries 

 numerous trap fragments. See special account. 



Division II. — Main Ridges. 



Locality 14. Section numbers, 1-4, 73, 76. Saltonstall Mountain. Percivai's Report, 

 pp. 323, 324. Percivai's notation, E. I. 



Saltonstall or Pond Mountain is the southernmost member of the 

 eastern main trap range ; it forms a well marked crescentic curve, with 

 Saltonstall Lake lying along the inner side. An under contact, lo- 

 cality 14', is found in the cut of the Shore Line Railroad, a quarter 

 of a mile east of Fair Haven station, and an upper contact is almost 

 revealed at the eastern end of the same cut. The back of the sheet 

 is very scoriaceous all along the shore of the lake, but no upper con- 

 tact is found until the northeastern end of the ridge is nearly reached, 

 when it is exposed in a little gully in the woods on the back of the 

 sheet over a pasture, locality 14 (Fig. 2). 



The trap is porphyritic and was originally glassy ; at lower contact 

 with sandstone, the trap is brecciated, fine-grained, and glassy ; slightly 

 vesicular ; vesicles elongated, indicating flowage action. Very vesicular 



1 W. North Rice, Amer. Journ. Science, XXXII , 1886, pp. 430-433. 



