246 The Physical History of the Trias 



tion of the old estuary, — can be judged by the igneous rocks ift 

 the two areas under consideration. In New Jersey, the Palisade 

 range is a hundred miles in length and several hundred feet 

 high. The parallel concentric ranges in the central portion 

 of the state, are each nearly fifty miles in length, and of great 

 thickness. The outcropping edges alone of the trap sheets in 

 New Jersey cover an area of 130 square miles. In the Con- 

 necticut Valley, the intrusive rocks are on an equally grand 

 scale. 



From our determinations, the outbursts of trap occurred 

 after the sedimentary rocks had been consolidated and up- 

 heaved, and at the time when the elevation terminated. With 

 this thought before us, we can understand the connection which 

 plainly exists between the trap rocks of New Jersey and those 

 in the Connecticut Valley, all of which must have been forced 

 out from a common reservoir and have a corresponding his- 

 tory. Here, too, we find the reason why the trap sheets are 

 confined to the red sandstone area, and are unconnected with 

 any other system of eruptive rocks. The peculiar "canoe- 

 shape," which these trap ridges present, is only intelligible 

 when we remember that the molten rock, after escaping 

 through the fissures in the floor of the estuary, would find its 

 way to the surface along the lines of least resistance, which are 

 now projected on the surface by the ridges of trap. 



General Considerations. 



We are fully aware of the extent of the areas, the magnitude 

 of the forces, and the great lapse of time, implied in such an 

 interpretation as we have given of the Triassic history. As 

 we have said before, the only way by which we can avoid 

 these vast proportions, is the possible occurrence of faults in the 

 Triassic rocks, which may have caused us to reckon the thick- 

 ness of certain strata more than once. Until plausible reasons 

 are shown, however, for suspecting such faults to exist, we are 

 obliged to reckon the thickness of these rocks in the usual man- 

 ner. From the dip of the beds and the breadth of country across 



