104 



tract the valley of the Flaikill, cut off from the river by a parallel 

 belt of fossiliferous limestone, the lower member of Forma- 

 tion VIII. 



These red sandstone rocks appear not to reach the Hudson ; 

 but, in the opposite direction, they extend a vast distance to the 

 southwest, where they are largely developed, as they likewise are 

 along the southern side of Lake Ontario. 



Composition and Structure. — The features of this formation are 

 considerably less diversified where it ranges across New Jersey 

 than where it rises to the surface in some of the other States. 

 The particular belt which follows the base of the Kittatinny 

 Mountain is marked, indeed, throughout its whole course, by 

 very little variety in the composition and appearance of the rock. 

 Its more variegated aspect is confined to the belts which lie 

 at a considerable distance to the northwest. As it occurs in 

 New Jersey, this rock consists, in its lower beds^ of a dark-red 

 sandstone of a very ferruginous composition and extreme hard- 

 ness ; and in the middle and upper divisions of the stratum, of a 

 brownish-red shale, and a very argillaceous sandstone, which are 

 sometimes slightly calcareous. These latter layers are occasion- 

 ally divided by thin bands of a different colour, commonly 

 greenish or yellow, but of the same composition; which, as the 

 whole rock is much affected by cleavage, assist materially in the 

 determination of its dip. Throughout its entire range the forma- 

 tion exhibits the peculiar structure resulting from cleavage ; 

 this is particularly well developed in the neighbourhood of the 

 Delaware Water Gap ; where it offers some interesting pheno- 

 mena to the geological student. An anticlinal axis of considerable 

 magnitude traverses the formation for several miles, ranging 

 immediately northwest of the Water Gap, disturbing the rocks 

 from their usual northwest dip, and giving to them a series of 

 undulations, distinctly traceable by aid of the lighter-coloured 

 bands above mentioned. Notwithstanding these irregularities, 

 the direction of the dip and strike of the cleavage surfaces con- 

 tinues every where the same, only slightly modified in their incli- 

 nation to the horizon, where the cleavage and true stratification 

 nearly coincide, in which case the latter exerts some influence. 

 The usual dip of the cleavage is to a point between south-south- 

 east and south, conforming entirely in angle and direction to 



