Ancient Sea Margins. 325 



Potomac and Rappahannock, which, besides being from sixty to 

 seventy feet 



a perfect counterpart to many examples of the terrace at the 

 same height on the British coasts. There are even more striking 

 coincidences than these. The gravel plain at West Point, if it can 

 be considered as connected with the sea margin of a former era, is 

 in harmony with one of the greatest of the British terraces. Nay, 

 among the elevated terraces which Mr. Roe has described as stretch- 

 ing along the sides of Lake Ontario, there are some which come 

 surprisingly near to certain similar formations which others have 

 described in this country. There may be nothing here but acci- 

 dental coincidence ; indeed it may be admitted that most prob- 

 ably there is nothing else in the case. It were well, nevertheless, 

 to make sure. 



For this purpose, I now beg to suggest to the geologists of 

 America, the propriety of examining such examples of ancient 

 beaches as may be within reach in their several districts, with a 

 view to settling the question one way or another. To all in 

 America who have written on kindred subjects, I would re- 

 spectfully recommend this inquiry, than which none could be 

 wore easily conducted. The first point should be, to find other 

 instances of the sixty-four feet beach ; in this country it is usu- 



ally a broad terrace of sandy or gravelly materials, presented 



towards the sea or along the banks of tidal rivers. If really a 



general feature of America, as of Britain and Ireland, I should 

 expect it to be found in many situations along the banks of the 

 Hudson. An examination of the form and constitution of this 

 terrace will fit the enquirer for discovering the higher bearhes ; 

 to which, however, I do not think it proper to attempt affording 

 a ny guide by the elevations of those found in Scotland, as ob- 

 viously, if there be any correspondences these will have more 

 force as evidence, if we can say that the two sets of facts were 

 arrived at independently. I shall only remark that terraces be- 

 tween one hundred and fifty and three hundred feet are more 

 hkely to be efficient as tests than any of lower altitude excepting 

 wly the sixty-four feet beach, because in that higher range of ele- 

 ctions the intervals are wide and more characteristic. Accurate 

 Measurements by levelling from a certain specified datum are of 

 co «rse desirable, and the results should be published from time 

 to time. I need scarcely say how much gratified I should feel by 

 ^y communications to myself upon the subject. 



