340 SCIENTIFIC RECORD FOR 1882. 



mark probably the channels through which the material of the great 

 sheets was brought up. They have produced a very limited alteration 

 proportionate to their breadth, of the adjacent strata. The beds of 

 trap of the second class have altered the sedimentary strata both above 

 and below them, and are not accompanied by amygdaloids. To this 

 class belong, according to Davis, the Palisades of the Hudson and the 

 range from West Eock northward near 'Sew Haven. To this may be 

 added a great dike at Lambertville, on the Delaware, above which 

 tourmaline, epidote, and specular iron have been developed in the 

 sandstone. The existence in the regions in question of trappean 

 masses of the third class, or overflows, has not been generally 

 recognized, although maintained by Edward Hitchcock for the Con- 

 necticut Valley, and also by Dawson for the Trias of l!^ova Scotia. 

 These subaerial or subaqueous beds are generally very amygdaloidal in 

 their upper portions, and sometimes at their base. The underlying sed- 

 imentary rock is but slightly affected, and the overlying bed not at all. 

 Tufaceous layers sometimes accompany these overflows, and fragments of 

 trap are occasionally found in the overlying sediments. These, as Daw- 

 son has shown, are frequent in Nova Scotia. Examples of these over- 

 flows are seen in Mounts Tom and Holyoke, in the Connecticut Valley, 

 and in their continuation in the Hanging Hills of Meriden; also, as 

 lately shown by Professor Emerson, in the Deerfield mass. Davis next 

 proceeds to consider the question of the general monoclinal arrange- 

 ment of the strata in the two Triassic areas in question, the dip in the 

 Connecticut Valley being to the eastward at angles generally from 10° 

 to 20°, and more, and in New Jersey and Pennsylvania to the westward, 

 with a similar inclination. H. D. Eogers supposed an original obliquity 

 of deposition; Kerr, a broad anticlinal fold in originally horizontal 

 strata, the belts of eastward and westward dipping beds representing 

 respectively the eastern and western portions of such anticlinals, from 

 which the remainder had been removed by erosion; while E. Hitchcock 

 and Le Conte imagined a simple monoclinal tilting. This would involve 

 an enormous thickness of strata, amounting, as Persifor Frazer has 

 shown, to over 50,000 feet for one measured section in Pennsylvania, a 

 conclusion for many reasons inadmissible. In the view of Davis, lateral 

 compression of the horizontally deposited beds produced a series of 

 folds with peculiar distortion, having the form of long, " shallow oval 

 dishes or boats, of gentle curvature, canted over a little, and faulted 

 on the side of the general monoclinal dip." A careful study of the over- 

 flows has enabled him to establish well-marked horizons, and thus sat- 

 isfactory evidence is obtained that the strata have been both folded and 

 faulted. In this way is explained the general crescent-like forms of the 

 trappean beds, which everywhere present their convex sides to the up- 

 ward slope; that is to say, westward in the Connecticut VaUey and 

 eastward in New Jersey. The great intruded sheets of trap which occur 



