1893.] NEW YOKK ACADEMY OF SCIENCES. 197 



bed of the Atlantic ocean.* On the land side this i)liiin was 

 bounded by the crystalline and Tiiassic rocks of Connecticut, 

 southern New York, New Jersey, Pennsylvania and southward, 

 as may be seen by an examination of any good geological map 

 of the eastern United States. The evidence of its extension 

 northward around Iihode Island and Massachusetts are now 

 almost obliterated, but there seems to be every reason to believe 

 that its laud limits were approximately the coast line of the 

 present day. In fact, a small isolated portion of the old coastal 

 plain still exists apparently in the vicinity of Marshtield, Mass., 

 as indicated by Edward Hitchcock in 1841 f, and recently by 

 N. S. Shaler, in a paper read before the Geological Sociely of 

 America. I It might also be added, by way of parenthesis, that 

 similar indications are to be looked for elsewhere, notably on 

 Ciipe Cod and near Gloucester, esi)ecially in case it should be 

 determined that MmjnoUa (jlaaca is truly native at this latter 

 locality, although Prof. Shaler does not mention any such in his 

 account of the geology of Cape Anu.§ Further north than 

 Massachusetts, so far as I am aware, it is not even indicated, 

 and except for the presence of the well-recognized submerged 

 plateau off our eastern shores all further trace of the former 

 coastal plain is lost. Its eastern limits, where it formerly met 

 the waters of the Atlantic ocean, were probably where we now 

 find the borders of this plateau to be, namely, at the lOU fathom 

 contour. 



Shortly after the advent of the Ice Age the elevation had 

 reached its maximum. The rivers had previously cut deep 

 valleys through the easily eroded material forming the coastal 

 plain, in their courses to the sea, and when the continental 

 glacier, pushing its Avay southward and eastward, finally flowed 

 over the edges and escarpments of the hard crystalline rocks 

 onto the soft and incoherent material of the coastal plain it 



* Up to thi.s point I believe all authorities are aKroed. In roKard to .suljse- 

 (luout KeolOKical ehanKos, and the interpretation of certain recognized facts, a 

 variety of views are held, many of them contradictory to one another, po tliat 

 an inii)artial statement, without more or less discu-sion, bec^omes almost an 

 inu)ossibility. I shall, therefore, set forth my own views freely, with iiriof 

 references to those of others, loavinti further discussion of the subject for some 

 future papers, which are now in course of preparation. The present contribu- 

 tion, so far as the ^eoloKV is concerned, may therefore be considered as a pre- 

 lude, and many points which are here somewhat summarily treated, it is hoped 

 to consider more fully later on- 



t '■ Final Itept. Gool. Mass." ii., 427. 



t " Tertiary and Cretaceous Deposits of Eastern Massachusetts.' (Dull 

 Geol- Soc Am. i., 443-452.) 



§ 9th Ann. Kept. U. S. Geol. Survey, 528-611. 



