248 GLACIAL FOKMATIONS OF ERIE AND OHIO BASINS. 



Lawrenceville station, on the Pennsj^vania Railroad, is a well-developed terrace 

 which extends to the West Penn Medical College. At Bi'ereton and Dickson streets 

 its height is 195 feet; at Thii-t_y -third street it is some 10 feet higher. The Bedford 

 Avenue water basin, near the Union railroad station, was excavated in part from a 

 terrace which at that point is 178 feet in height. Several houses which were built 

 on the original terrace before the avenue was graded still remain. This terrace, 

 extending from the water basin around the hill to Crawford street, though now 

 covered with houses, can be traced without difficultj^ hj an examination of door- 

 yards, wells, and other excavations. On Fulton street, at the foot of Center avenue, 

 its height is now 194 feet. * * * 



The great canyon of the Ohio has formed an amphitheater at Pittsburg nearly 

 3 miles long and more than 1 mile wide. This amphitheater is completely surrounded 

 by high cliffs, except the narrow gorge on the east through which the Allegheny 

 enters, and the one on the west through which the Ohio departs. On the walls of 

 this amphitheater are two distinct horizontal lines; the lower one, as we have seen, 

 appears in many places from 140 to 160 feet above the river, while the upper is a 

 well-marked shelf or terrace 200 feet above low-water mark in the Allegheny. 

 Directly connected with the 200-foot level is the ancient river bed of the Mononga- 

 hela, which at one time ran through the East Liberty Vallej'. It entered the valley 

 a few miles below Braddock's, passed a little to the west of Swissvale and Wilkins- 

 burg railroad stations, through Brushton, Homewood, East Liberty, and Shadyside 

 to Herron's Hill. This hill presented an insurmountable barrier to its further 

 progress in this direction, and here it divided, the left branch forming the plain on 

 which so ma.nj beautiful houses in Bellefield and Oakland have been built; the other 

 passed to the right of the hill, joining the Allegheny. Through its whole course we 

 find well-marked evidence of river action — huge bowlders, smoothed and rounded by 

 being rolled over and over in the bed of the river; great banks of sand and gravel 

 distinctly stratified; large heaps of cobblestones and other characteristic marks. 

 The position of the bed-rock is determined, not onlj^ by outcrops at the beginning 

 and end of the vallej', but also b}^ the sides of the railroad which passes through it, 

 and by numerous wells and other excavations. Ditches dug for sewers, water, and 

 gas pipes show the greatest depth of the deposit to be from '20 to 25 feet near the 

 middle of the vallej^ graduall}^ growing less in depth towards the sides. Another 

 evidence of river action is shown by a well-defined "second bank," which runs along 

 the southern side a distance of more than 2 miles. On this second bank is now 

 located Fifth and Penn avenues from Shadyside nearly to Wilkinsburg. From the 

 top of this bank to the Pennsylvania railroad track is an abrupt descent of many feet. 

 Before Peon avenue was graded a person going from East Liberty to Wilkinsburg 

 soon made a steep ascent at Point Breeze hotel, reaching the top of this bank. Passing 

 along it nearly to Wilkinsburg, at the old "yellow tavern" on the left, he plunged 

 into the old river bed, cros.sing which he reached his destination. At Homewood 

 and Penn avenues this second bank is now 79 feet above the ancient river bed; at 

 Fifth and Shady avenues, 71 feet; and at Amberson and Fifth avenues, 54 feet. 



Before leaving East Libert}^ Vallej^' let me call your attention to a point of con- 

 siderable importance. The great deposit of gravel containing foreign material, in 

 Alleghen}' Cemeter}', extends into the East Libert}^ Valley, and was deposited on the 



