Eolian Action in Southern JSFew England. 71 



process of sand-carving is now evidently going on ; but I am 

 led by the distribution of many of the pebbles which I have 

 collected to think that sand-blasting was formerly more preva- 

 lent than it now is in this district. 



Relation of land to sea-level. — It is obvious that the carv- 

 ing and polishing of rock surfaces by the sand-blast is essen- 

 tially a subserial phenomenon. Although the sand carried by 

 water-currents as in the case of the Colorado, shown by New- 

 berry, furrows and polishes the rock of its bed, the sands of 

 the littoral are not known to produce the facets and polish 

 characteristic of the typical glyptoliths. This is probably due 

 to the frequent turning and rubbing of pebbles even where 

 they lie in the zone of sands driven by wind along the beach. 

 It follows that where we have these eolian pebbles carved at 

 any time in the past, we have evidence to show that at that 

 time the land was above the level of the sea. As yet the 

 coast region of New England along which submergence at the 

 close of the last glacial epoch has been suspected has not been 

 examined with this point in mind.* The evident antiquity of 

 the Matakeset examples on Martha's Vineyard and the direct 

 superposition of the eolian pebbles on the wind-eroded surface 

 of the overwash or frontal plain indicates that next after the 

 deposition of the glacial gravels it was subjected to wind-ero- 

 sion. This evidence indicates that if the land there was sub- 

 merged after the retreat of the ice, the period of depression 

 was brief and is locally without any trace of its geological 

 effects. 



Among the problems which these eolian pebbles may be 

 looked to for a solution is the question of the former elevation 

 of the continental shelf in recent geological times. It is there- 

 fore of the utmost importance that the pebbles and bowlders 

 occasionally dredged up from the surface of the "banks" off 

 the New England coast should be carefully scrutinized with 

 the view of determining whether or not they bear marks of 

 eolian erosion. If, as there is reason to believe, these banks 

 were during late Tertiary or in the pleistocene period, like 

 Martha's Vineyard and Nantucket now, above the sea-level, 

 we should find on them the kind of evidence which occurs on 

 the islands named. 



Cambridge. Mass. 



* Since 'this was written, Prof. W. M. Davis has presented in the current vol- 

 ume of the Proc. Boston Soc. Nat. Hist, a paper announcing the occurrence of 

 facetted eohan pebbles at numerous points on Cape Cod in geological situations 

 showing the subserial deposition of at least a part of the glacial gravels of that 

 peninsula. See also paper by the same author read at the December meeting of 

 the G-eol. Soc. Am., held in Boston, 1893. 



