REVIEWS. 743 



stratigraphy; in which the various kinds of rocks are enumerated, but 

 in which their succession and thickness is not stated. The difficulty of 

 the problem lies in the monotony of the strata, and in the doubt in 

 many cases as the origin of the trap sheets. Whatever success has yet 

 been gained in solving this problem, it has come chiefly through the 

 aid given by the old lava flows, and only secondarily through ordinary 

 stratigraphic methods. In Pennsylvania and further south, no com- 

 plete stratigraphic correlations have yet been established ; mainly, as 

 has has been stated above, because the trap sheets there are not yet well 

 deciphered. In New Jersey the discrimination between intrusive and 

 extrusive sheets has been well accomplished, but doubt is felt as to 

 the location of fault lines by which they are dislocated, this doubt 

 resulting from the uncertainty as to the reappearance of identical sand- 

 stone strata or trap flows. It is only in the Connecticut valley that 

 the variety of trap sheets and associated sedimentary beds is such as to 

 make the demonstration of faults complete. Here, over a considera- 

 ble share of the area, the stratigraphic succession is made out with much 

 certainty; and the lines of dislocation are determined with sufficient 

 precision. At the same time certain fossiliferous beds, rare in the for- 

 mation as a whole, and therefore of all the more value in defining hori- 

 zons, have been traced for thirty or more miles inland from Long Island 

 Sound; and their dislocations agreeably confirm the conclusions pre- 

 viously reached as to the faulting of the trap sheets. 



Like so many other features of this peculiar system of rocks, its 

 style of deformation is exceptional. It is nowhere folded in the ordi- 

 nary manner; where curvature of bedding appears, it is of such char- 

 acter as to give crescentic outlines to the beveled edges of the strata 

 now visible. The formation is, as a rule, tilted over to a rather regu- 

 lar monoclinal attitude; but while the earlier conceptions of its struc- 

 ture implied that the monocline was practically uninterrupted, the later 

 studies show it to be complicated by numerous faults, traversing the 

 mass in various directions, and as a rule systematically arranged, 

 although the control of the system is obscure. One thing is clear : the 

 faults penetrate the crystalline foundation on which the Newark beds 

 lie; they are not dislocations within the Newark beds alone; indeed, it 

 almost seems fair to say that the dislocating forces were indifferent to 

 the cover of Newark beds, and that their action was chiefly expended 

 on a much deeper mass of rocks 



The original extent of the Newark areas has been much discussed, 



