306 BULLETIN OF THE 



trend of the trap ridges (430-432). Hitchcock noted the same arrange- 

 ment for Massachusetts (e, 654; h, 17, and PI. II.), and Cook mentions 

 it for New Jersey (c, 29, 32). 



An iHustration of a flat fold producing a curve may be seen in the 

 excellent example at Beckley, Conn. (D) ; it corresponds perfectly with 

 the much larger curves shown by the Turner's Falls — Deerfield Range, 

 by the great range from Belchertown, Mass. to Meriden, Conn., by 

 many other smaller ranges in Connecticut so well shown on Percival's 

 beautiful map, and by several similar curves in New Jersey. The most 

 instructive region for the further study of this important point in the 

 structure of the Triassic belts is without doubt the southeastern corner 

 of the Connecticut sandstone area, about Durham and North Branford, — 

 Percival's "volcanic focus" (311). I had hoped, but was unable, to 

 reach it during the past summer. 



All these folds are like flat oval dishes, tilted toward and faulted on 

 the dip side of the general monoclinal ; and as a necessary consequence 

 of this, the trap sheets that are folded with the sandstones outcrop in 

 crescentic ridges with the horns of the crescent pointing in the direction 

 of general dip.* The fact of this position was first published by Percival 

 in 1842 (311), but its cause was not then perceived. The folds are 

 very numerous in Connecticut, but in Massachusetts and New Jersey 

 they are fewer and larger : this would indicate that in the last two States 

 there is the nearest approach to the simple monoclinal of the third 

 theory of disturbance. An interesting exception to the rule occurs east 

 of Saltonstall Lake, Conn. ; it is P. 2 of E. I. of Percival's notation, and 

 is described as abrupt on its eastern, convex side (325) : this makes it 

 seem very much like the eastern edge of a small sheet whose western 

 outcrop is lettered P. 1 on Percival's map. Whether the small curves 

 in southern Durham lettered P. 1 of E. III. are produced by folding, or 

 result from the original form of intrusion or overflow, or are simply the 

 effects of erosion, requires furtlier observation to detei'mincf 



In regard to the crescentic form of the trap ridges, H. D. Eogers con- 

 sidered it natural that the horns of the curves should point with the dip 



* The imitation of this crescentic line of outcrop produced at a ci'oss valley is men- 

 tioned under the observations at Beckley. 



t It is greatly to be regretted that Percival had not the facilities for illustration 

 afforded now by well-executed ehromo-lithography. A map of the Connecticut valley 

 drawn with as full an appreciation of topographic form as Percival must have pos- 

 sessed, and colored to show the different varieties of trap and sandstone, is needed to 

 do justice to the remarkable features of this unique region. There is nothing like it 

 known anywhere else in the world. 



