B Report on the projected Survey of the State of Maryland. 



ent ; and the cliffs, between Drum point and Cove point, in Calvert 

 county, present a vertical section of about seventy feet, consisting in 

 the descending order of; 1st. Gravel and sand, fifty feet in depth. 

 2d. A bed of marine shells, in the upper portion of which the shells 

 are firmly bound together by a ferruginous cement, and in the lower 

 portion are imbedded in a blue clay : this bed measures upwards of 

 ten feet. 3d. A tough blue clay, rising ten feet above the level of 

 the bay. 



The localities at Indian point and Maryland point are stated upon 

 the authority of intelligent gentlemen, who have asserted the exist- 

 ence of shell deposites on those spots ; but the deposite on the Saint 

 Mary River having been examined by the undersigned with some 

 <;are, they are enabled to specify some circumstances connected with 

 it, of great interest, (it is thought,) both in a scientific point of view, 

 and in consequence of the practical application which naturally, in 

 ihose circumstances, suggests itself. 



The deposite referred to occurs at the mouth of Saint Inigoe's 

 -creek, on the western side. It is overlaid by a bed of ferruginous 

 sand, soil and gravel, about twelve feet thick. The shells are very 

 abundant, and present a great variety of genera and species. They 

 occur in a blue clay, and are associated with groups of crystallized 

 selenite, which project from the bank through the clay from one to 

 two feet above tide ; or after high tide, having been washed out of 

 the bank, are loosely scattered over the beach. This bed of clay 

 contains likewise small pieces onignite, nodules o( ii-on pyrites^ (sul- 

 phuret of iron,) and, whenever exposed to the influence of atmos- 

 pheric agents, becomes covered with an efflorescence of copperas, 

 (sulphate of iron.) 



The formation of the selenite (which is the name given to the pu- 

 rest variety of a well known mineral employed in agriculture and the 

 arts, as plaster of Paris,) merits consideration in a two- fold respect, 

 scientifically and practically. 



It is not difficult to account for the formation of this variety of plas- 

 ter of Paris, under the circumstances which have just been stated to 

 be peculiar to the locality mentioned. Selenite is a compound of 

 sulphuric acid and lime. In the language of chemistry, it is a sul- 

 phate of lime. Its constituents occur abundantly in the bed of clay 

 which has just been described — the sulphuric acid being derived from 

 the decomposition of the iron pyrites and copperas, and the lime from 

 that of the shells. Their spontaneous union, under a variety of fa- 



