302 C. N. FENNER 



the Watchung traps and ascertain to what extent their structure bears 

 out the theory of continental origin. We find that they form a monot- 

 onous series of shales, sandstones and conglomerates, composed 

 mostly of quartz fragments. Sufficient oxide of iron is usually present 

 to give a reddish, brownish, or purplish color to the whole. Feld- 

 spathic material is often visible, and the derivation of all these is 

 plainly referable to the crystalline areas on the East or West. In 

 addition to these we find in many of the coarser layers plentiful pebbles 

 of limestone, up to six inches or more in diameter, whose source is 

 obscure. 



In observing carefully the succession of strata in this series one is 

 at once impressed with the lack of continuance of the beds in any 

 direction and the variation in the succession at different sections along 

 the same horizon. Within a distance of a few hundred feet the 

 character of the section may change markedly. This may be brought 

 about in three ways. 



1. A bed may gradually thin out and disappear. This is especially 

 true of the sandstones. 



2. The size of the fragmental material may alter in a pronounced 

 manner, while the thickness of the stratum remains approximately 

 the same. The proportion of pebbles in a bed of sandstone or even 

 of shale may increase or diminish rapidly. This is generally brought 

 about, however, by the intercalation of pebble beds in the sandstone 

 layers, rather than by a general increase in the coarseness of all the 

 material. 



3. A given stratum may be cut sharply away, and different material 

 abut against it. 



All these variations are shown in the gorge of the Passaic River, 

 a short distance below the falls at Paterson. Fig. i is from a sketch 

 made just south of Ryle Avenue. Two very irregular bands of shale 

 {a and h) cut sharply downward across the sandstone and pebble beds, 

 and are overlain by strata differing from those in the same horizontal 

 planes on the right. It appears evident that a water-course has cut 

 its way through previously deposited strata, and the valley thus formed 

 has later been filled by water-borne sediments or wind-blown sands 

 until a level was again reached and a more orderly course of deposition 

 was continued across it. The pot-hole at (c) filled with gravel, stones, 



