1886.] natural sciences of philadelphia. 253 



May 4. 



Mr. Geo. W. Tryon, Jr., in the chair. 

 Twenty-pight persons present. 



The Railway Gutting at Graifs Ferry Road. Mr. Aubrey H. 

 Smith remarked that the Schuylkill River, as is well known, 

 makes a curve to the westward just below the TJ. S. Arsenal 

 grounds, returning to its southwardly course at Harmar's wharf, 

 nearly a mile below. The new iron bridge of the Baltimore and 

 Ohio R. R. Co. spans the river obliquely from the northern side 

 of Bartram's Garden to Harmar's at the height of about 23 feet 

 above tide. The tract of land half enclosed by the river is ele- 

 vated about 50 feet above tide and is composed of the same 

 diluvial gravels and clays which form the plain on which stands 

 the old city of Philadelphia. 



The railroad proceeds from the bridge by a deep cut of half a 

 mile transversely to the streets on the city plan northeastwardly 

 to the low grounds on the river below the arsenal, thus forming 

 a chord to the arc of the river bend. The cut is a deep one, as 

 the railroad company was required by its agreement with the city 

 to construct its line beneath Wharton Street and the Gray's Ferry 

 Road. 



Soon after leaving the bridge the cutting enters the plateau and 

 is soon twenty-five or more feet deep. The excavation is through 

 yellow cla3'^s and river gravels to the depth of about twenty -five 

 feet. It then discloses a compact bed of dark blue clay, sharply 

 defined under the gravel, apparently a river deposit. Its thick- 

 ness is not exactly known but it exceeds six feet. This bed of 

 blue clay extends from just bej'ond the Harmar house to the 

 Gray's Ferry Road, a distance of 500 or 600 yards. 



It is apparently thickest near the Harmar house, but thins out 

 at the Gray's Ferry Road, where the excavations show it to be 

 only about four feet thick and to rest uj^on a bed of yellow gravel 

 or sand. It does not appear at all northeast of the Gray's Ferry 

 Road. 



Some observations and inquiry in November, 1885, for organic 

 remains resulted, so far as he was aware, only in showing that 

 the blue clay contains numerous genera and species of diatoms 

 and several species of recent woods. The observations on the 

 diatoms are due to Professor Koenig. The gravels and cla3^s 

 above the blue clay were barren of all organic forms. The woods 

 then obtained were apparently birch, maple or oak, and were 

 neither mineralized or decomposed. They came from the dump 

 heap where the excavated clay was deposited by the workmen, 

 but are doubtless from the blue clay bed. 



