NATURAL SCIENCES OF PHILADELPHIA. 291 



accumulations extending from just below the town of Lewes on Delaware Bay, 

 for about the distance of a mile or more to the base of a huge sand dune be- 

 tween the bay shore and the light-house of Ope Henlopen. Tbey had provided 

 themselves with ample means to examine the extent of the shell heaps, and 

 had been surprised to find that they were all quite superficial, from a few 

 inches to less than a foot in depth. In a number of places they appeared to 

 form hillocks, but they were only accumulations around the former sites of 

 trees, as indicated by the traces of stumps and roots. 



They visited 'similar accumulations on the shore south of the Cape, and were 

 told that they were found in many positions down the coast. 



All of those which were examined contained fragments of pottery, chips of 

 jasper, and stone arrow-heads. A few copper rings were also found, and in 

 one heap Mr. Canby found several English coins. 



Dr. Leidy thought the shell-heaps were of no great age, and were probably 

 coteruporury with the discovery of the country by Europeans. 



October 30th. 



Mr. Vaux, Vice-President, in the Chair. 



Twenty six members present. 



Drs. William Mayburry, and W. C. Dixon were elected members. 



Dr. Haj r den, having just returned from a tour of exploration to the " Mau- 

 vaiscs Terres," or " Bad Lands " of White River, made some remarks in 

 regard to a side trip to the celebrated Pipestone quarry of North-eastern Da- 

 kota. He spoke of the locality as very inconspicuous, and that it would have 

 hardly attracted attention had the existence of this Pipestone bed not been 

 known to exist there. Not a tree is to be seen in the region round about, only 

 a few small bushes growing among the rocks. There is an escarpment, or 

 nearly vertical wall, extending across the valley of Pipestone creek nearly a 

 quarter of a mile either end of this wall, gradually passing from view beneath 

 the prairie. The entire thickness of the rocks is about 50 feet. The Pipe- 

 stone layer is about 11 inches in thickness; about 2|- inches is homogenous 

 and compact enough to be used by the Indians for the manufacture of Pipes. 

 The remainder is of various colors and texture, from a deep red to a cream, and 

 oftentimes mottled. The rock is soft, slaty, fragile, and underneath the Pipe- 

 stone is a bed of close-grained grey quartzite ; above there is about 6 feet of 

 the same rock, which must be removed with great labor before the precious 

 material can be secured. Still higher are 40 or 50 feet of reddish and varie- 

 gated quartzites, which, like the pipestone itself, are colored with peroxide of 

 iron. 



It is difficult to come to any positive conclusion as to the age of these rocks, 

 from the fact that no well defined organic remains could be found. It is the 

 opinion of the eminent geologist, Prof. Hall, that they belong to the Iluronian 

 series, and, from his large experience among those rocks, and the fact also that 

 he describes similar quartzites at a point within 60 or 70 miles of the quarry, 

 entitles his opinion to great weight. Rocks of the same age occur at Sioux 

 Falls, and upon the smooth surfaces may be seen, in great numbers, the out- 

 lines of what appear to be bivalve shells, but so close grained is the quartzose 

 matrix that no well-defined shell could be broken from it. If these rocks are 

 really charged with fossils, we are led to look higher in the geological scale for 

 the true age of the Pipestone bed. 



Dr. H. remarked, in regard to the time of the opening of this quarry by the 

 Indians, he does not think they had any knowledge of the rock far back in the 

 past. No trace of stone implements were discovered in the vicinity, and he 

 could not ascertain that any had ever been found. Mr. Vaux, Vice-President 

 of the Academy, has examined large collections of stone implements and orna- 



1866] 



