30 NEW YORK STATE MUSEUM 



accumulations have obliterated its topographic relief. Eastward 

 and westward however it becomes prominent. A drive along Main 

 street from BufTalo to Akron at the Erie county line will reveal the 

 fact that it gradually increases in hight and boldness, till at the 

 latter place it rises nearly a hundred feet above the Tonawanda val- 

 ley, which itself is drift filled to a not inconsiderable extent. If we 

 trace this escarpment into eastern New York, we find it progress- 

 ively increasing in hight^ owing to the interpolation, between the 

 Manlius and Onondaga limestones, of the thick beds of the Helder- 

 bergian series^ which, with the other lower Devonic beds, are 

 entirely absent in the Niagara region, where their place is marked 

 by an unconformity. (See figs.i and 21-24) 



If the observer changes his position to some elevated point near 

 Buffalo, he may note that the plain which extends southward from 

 the edge of the second escarpment, presents again a scarcely modi- 

 fied and almost level surface, which south of Buffalo gently de- 

 scends to a third lowland, that of Buffalo creek and Lake Erie. 

 Like the other lowlands, this one is carved out of soft rocks (Mar- 

 cellus and Hamilton shales) and has subsequently been filled to 

 some extent b}^ drift deposits. This has been proved by borings 

 which show that the bedrock in the valley of Buffalo creek is 83 

 feet below the surface of Lake Erie.^ There are other excellent 

 reasons for believing that the western end of this lowland, now occu- 

 pied by Lake Erie, was once considerably lower than at present. 



On the south the Erie lowland is defined by a range of hills, the 

 northern edge of the great Allegany plateau, which forms the high- 

 lands of southern New York and northern Pennsylvania. There 

 are no very pronounced declivities in the northern edge of this 

 plateau in the Lake Erie region, owing no doubt to the relatively 

 uniform character of the rocks composing it, there being no re- 

 sistant capping bed of sufficient magnitude to produce an escarp- 

 ment. Farther east, however, owing to the increasing thickness of 

 the beds and their more resistant character, a prominent escarp- 

 ment is developed, which near the Hudson unites with the escarp- 

 ment of the lower series, and with it constitutes the prominent Hel- 



^Pohlman. Life history of Niagara- 1888. p. 4. 



