242 The Physical History of the Trias 



"Washington Valley, in which the red sandstones and shales ap- 

 pear, with their usual dip toward the northwest. For further 

 details of the geographical features of these trap ridges, we 

 must again refer the reader to the geological reports of Profes- 

 sors Rogers and Cook. 



In the Connecticut Valley, we find another series of trap 

 hills traversing the Triassic formation of that section.* These 

 ridges, like those in New Jersey, are usually sheets of igneous 

 rock conformable with the associated sandstones and shales. 

 As we have already seen, the sedimentary rocks in these two 

 areas dip in opposite directions, and consequently the trap 

 ridges slope gently to the eastward in the Connecticut Valley, 

 and present steep mural escarpments facing the west. Like 

 the ridges in New Jersey, also, those in the Connecticut Valley 

 show a curved outline, but the convex side is towards the west, 

 while the ends are bent sharply eastward, and like the New 

 Jersey trap ridges, end abruptly when they approach the crys- 

 talline rocks. All these features are apparent at a glance upon 

 examining a geological map of these regions ; and we also see 

 that the trap rocks are almost entirely confined to the area 

 covered by the Triassic sedimentary beds. 



The trap rocks of New Jersey and the Connecticut Valley 

 are also nearly identical in their lithological peculiarities. Thev 

 are usually composed of an intimate combination of hornblende 

 with some form of felspar, forming different varieties of dole- 

 ryte, diabase, etc. At times they are amygdaloidal, and con- 

 tain quartz, calcite, and a great variety of zeolites, in their 

 cavities. Again, they become basaltic in structure and form 

 prismatic columns. Besides these indications that the trap rocks 

 have cooled and consolidated from a state of fusion, we find 

 also that in many cases where the shales and sandstones come 

 in contact with these erupted rocks, the former have been 

 changed from their normal condition and greatly metamor- 

 phosed both in color and structure. The occurrence of indu- 

 rated shales associated with trap, is mentioned by Percival in 



*For details see Hitchcock's Geol. Rep. of Mass., and Percival's Geol. Rep. of Conn.. 

 1842. 



