Association of American Geologists. 169 



At the mouth of Pickawaxent Creek, about eighty miles below Wash- 

 ington, there is an extensive deposit of oyster shells, at which an establish- 

 ment has been formed, which, in a ^ew months has converted many thou- 

 sand bushels of them into lime. Before any excavation of the mass was 

 commenced, I had directed the attention of Mr. Downing — one of the 

 partners concerned — to the doubtful nature of their origin, requesting 

 that all facts tending to throw light upon them should be carefully ob- 

 served and preserved. When Mr. D. first went into the country, he was 

 in favor of the views of Mr. Conrad ; it was only by the examination of 

 the mass at the Pickawa.xent, of another not remote from that one, and 

 from subsequent observation in the city of Baltimore, showing the amount 

 of shells which there accumulates, was he assured that their origin was 

 to be referred to man, and not to other or more elementary powers of na- 

 ture. 



The first and most important fact there observed, was that neither he 

 nor any of the hands employed in getting out the shells had been able to 

 find any two valves which fitted each other, excepting in one instance ; 

 a waterman having brought the specimen to him. The deposits having 

 the nature of a mass or heap composed of shells whose valves were sepa- 

 rated before being thrown together. 



That in many parts of the mass arrow-heads and fragments of pottery 

 have been found in the progress of excavation — these in no wise different 

 from those found in old settlements of the Indians. 



That the bottom of the bed is formed of the yellow loam or soil of the 

 country, and that the roots and other parts of the cedar of the country 

 have been met with at the bottom of the bed, showing a growth upon the 

 surface, before the shells were deposited upon it. 



That these deposits are at the mouths of the creeks, extending up the 

 creeks, and rarely extending along the river shore, owing, as Mr. Down- 

 ing conjectures, to the excellent fishing which the creeks furnish, and 

 which would give to those who accumulated the shells, a twofold advan- 

 tage. 



That the shore is low on that side of the river where they are found, 

 and the recent oyster in great abundance on that shore, whilst the chan- 

 nel is on the Virginia side, and no deposit of oyster shells existed in that 

 section of country. 



That these deposits are of some comparative antiquity, is to be inferred 

 from the soil which is found upon them, and the existence of an exceed- 

 ingly old cedar growing upon the top of a mass, and from the silence of 

 history or tradition respecting them. 



Against these facts which show an undoubted human origin for these 

 deposits of oyster shells, there are others cited by Mr. Conrad which he 

 has made me acquainted with, since this paper was written, which either 

 I had not known or they had escaped my memory, and are equally con- 



Vol. XLi, No. 1.— April-June, 1841. 22 



