1876.] t>^ [Lesley, 



been made, the road-beds have been tempered up, or down, 

 to suit convenience, and no record of the fact been kept, ex- 

 cept in the memory of some division engineer no longer in 

 the employ of the Company, — it is surprising that the errors 

 of terminal or crossing adjustment are so few and small. 

 But to render the record perfect all such errors, however 

 few and small, must be eliminated ; and this can only 

 be accomplished by a zealous interest taken in the subject 

 by resident engineers ; who are therefore earnestly requested 

 to co-operate to this end. 



Geologists are dependent for the goodness of their field- 

 work on accurate base-line levels. And it is to be hoped 

 that a complete exhibition of the surface contour of Penn- 

 sjdvania will sooner or later be obtained from a collation of 

 the thousands of transit-lines and barometer-lines now in 

 progress in all the districts occupied by the Assistant Geolo- 

 gists of the Survey. All their lines of levels are, however, 

 based on the railroad, records, and the publication of these in 

 a corrected form is a necessary preliminary step. 



If movements are still taking place in the crust of the 

 earth, — and the frequent occurrence of slight earthquake 

 shocks, in all the States of the Union, seems to speak in 

 favor of the supposition, — physical philosophers are peculiarly 

 interested in an early establishment of a universal hypso- 

 metrical record. From this point of view, also, it would seem 

 especially germain to the origin and history of the American 

 Philosophical Society to initiate such a record. 



The net-work of Surveys which cover Pennsylvania 

 may be divided into nine systems : 



1. The Pennsylvania Central east and west system, from 

 Trenton through Philadelphia, Harrisburg, Altoona, Pitts- . 

 burgh, to Steubenville, and Youngstown, in Ohio ; with 

 numerous longer or shorter side branches. 



2. The Reading Railroad northwest and southeast system, 

 with many short branches in the Schuylkill Anthracite Field, 

 and through the country in front of it between the Delaware 

 and Susquehanna Rivera. It has been extended also to the 



