of the Eastern States. 243 



his report on the geology of Connecticut, and may be observed 

 at many points beneath the trap-sheets in the Connecticut Val- 

 ley. In New Jerse}', the proof that the trap rocks are truly 

 intrusive in their nature, is abundant. In this connection the 

 reader may refer to an article by the present writer, in the 

 American Journal of Science,* from which we quote the fol- 

 lowing passage : 



" It is not difficult to find the junction of these igneous rocks 

 with the shales and sandstones that underlie them. In all such 

 cases that have come under our notice, the stratified rocks have 

 been found to be highly altered, and show very plainly that 

 they have been exposed to intense heat. At a number of 

 places beneath the trap rock forming the Palisades on the 

 western shore of the Hndson, this change may be observed ; 

 in some instances the sandstone beneath the trap has been 

 metamorphosed into a compact vitreous quartzyte. At the 

 Falls of the Passaic, the junction of the igneous rocks with the 

 altered sedimentary rocks beneath, is well exposed. We have 

 also observed similar indications of the action of great heat at 

 a number of places in the shales and sandstones beneath the 

 trap rocks in the neighborhood of Plainfield, New Jersey." 



The proof that the shales and sandstone that rest upon the 

 trap have been metamorphosed and greatly changed from their 

 normal condition, is given in the same article. The observa- 

 tions prove definitely that the trap rock was forced out in a 

 fluid state between the layers of the sedimentary beds, and 

 altered the latter at the surface of contact, by the intense heat 

 to which they were exposed. The trap in some in some in- 

 stances appears as a true dike, breaking directly through the 

 stratified rocks and showing at a glance its intrusive nature. 

 An instance of this kind is described and illustrated in Profes- 

 sor Cook's geological report, f 



Ever since we commenced the study of the physical history 

 of this formation, we have been impressed with the manner in 



* " On the Intrusive Nature of the Triassic Trap Sheets of New Jersey." — Araer. J. Sei., 

 Third Series, Vol. II, p. 277 (April, 1878). 

 t Geology of N. J., 1868, p. 204. 



