254 



PROCEEDINGS OF THE ACADEMY OP 



[1886. 



The specimen of wood exhibited to the Academy to-night is of 

 some coniferous tree, probably a white cedar, Gupressus thyoides. 

 This tree, until verj^ I'ccently, was common along the Schuylkill 

 and Delaware, and isolated specimens may still exist there. The 

 wood now shown is in no degree mineralized and but slightly 

 decomposed. It came from a log which lies in the blue clay just 

 north of the Wharton Street Bridge and is still to be seen there. 

 No shells, so far as he knew, have been found in the excavation, 

 but more careful search in this direction might be rewarded. 



The blue clay bed appears to mark one of the periods of quies- 

 cence in the glacial action which, in its torrential course, scooped 

 out the valleys of the Schuylkill and Delaware and afterwards 

 filled them up again at the margin of tide-water. It harmonizes 

 itself with similar beds which have been observed at several points 

 along the shores of the rivers notably at the Lazaretto and 

 Printz Hall, Tinicum, and near Camden, N. J. 



There were probably several of these periods of comparative 

 rest in the course of the retirement of the ice from northern 

 Pennsylvania. 



The artesian well of Mr. Black, at Black's Island, below Fort 

 Mifflin, which is 456 feet deep, disclosed at the depth of 100 feet 

 a bed of white beach sand 47 feet in thickness, as well as many 

 of gravel and clay. The decomposed gneiss rock was reached at 

 the depth of 240 feet or thereabouts. 



Section of the strata of Black's Island, Delaware River below 

 Fort Mifflin, from the artesian well of E. N. Black, Esq. : 



Blue alluvium, . 



Sand, .... 



Blue alluvium, . 



Gravel, .... 



White clay, 



Beach sand, 



Gravel, .... 



Clay, .... 



Red gravel, 



White gravel and sand, 



Beach sand and gravel, 



Decomposed gneiss (mica), 



Gneiss rock, 



456 feet. 



May 11. 



The President, Dr. Leidy, in the chair. 

 Twenty -two persons present. 



Fatal Gases of Trichiniasis. The President read a letter from 

 Mr. Eugene A. Rah, of Bethlehem, Pennsylvania, giving an ac- 

 count of recent cases of fatal trichiniasis arising from imperfectly 



