1896.] NEW YORK ACADEMY OF SCIENCES. 17 



north. This naturall}' raises the question whether the chiys at 

 Grace Point and Ball's Point are in their original position, or 

 whether (which I consider more likely) they have been shoved 

 southward a greater or less distance, as we know has been the 

 case on Staten Island and Long Island, and probably on Mar- 

 tha's Vineyard and Nantucket. 



The absence of marl strata, from which the molluscs were de- 

 rived, yet requires a satisfactory explanation. The same prob- 

 lem also awaits solution on Staten Island and Long Island. 

 Normally, of course, these strata should outcrop between those 

 of the Tertiary and Cretaceous clays, and yet there does not 

 seem to be any record of their presence either at the surface or 

 in any well-borings. It has seemed to me probable that being 

 less plastic than the clays the marl was more easily eroded, and 

 consequently was broken up and dissipated instead of 3-ielding 

 in masses. 



Block Island has thus been brought into line geologically 

 with Long Island, Martha's Vineyard and Nantucket, as was 

 theoretically expected. The}^ all had their origin in one series 

 of cause and effect, and must be studied and regarded as a whole 

 in order to appreciate the full significance of the facts which are 

 now in our possession. 



They manifestly represent remnants of the former coastal 

 plain, which consisted of Cretaceous and Tertiary sands, gi'avels, 

 clays and marls. The glacier of the Ice Age squeezed upward 

 and pushed forward these incoherent strata into a series of con- 

 torted folds along its line of furthest advancement, depositing 

 on top the detritus of the moraine. The ridge so formed was 

 at first continuous, but with the gradual sinking of the coast, 

 and the action of the ocean, the less elevated portions have suc- 

 numbed, and only the highest parts, now represented by these 

 islands, remain above water. All the facts point to this con- 

 clusion, and even the most superficial observation shows that 

 the phenomena of submei'gence and erosion are in active oper- 

 ation at the present time. Should they continue in the future 

 it requires but little prevision to appreciate that Block Island 

 and the islands to the eastward will continue to shrink in size, 

 disappear, and eventuall^^ form merely parts of the shoals which 

 now connect and surround them. Montauk Point will continue 

 to recede, and, by the submergence of the low narrow strip of 

 land in the vicinity of Canoe Place, a new island will be formed 

 from what remains of the Point. 



These facts and conclusions, which appear obvious enough 

 now, have only been established by years of careful work, but 



Transactions N. Y. Acad. Scr., Vol. XVI., Sig. 2, January 22, 1897. 



