1877.] 21 (Carll, 
The two tables of the P. & E. levels (the Company’s and Burgin’s) given 
by Mr. Allen, in his R. R. levels of Pennsylvania, contain in themselves 
the evidences of inaccuracy. The Company’s profile datum is ‘‘ Mid tide 
Baltimore.’’ Burgin’s is P. R. R. datum on the east end and Lake Erie 
based on ocean on the west end (but now shown to be 11/ too low), yet both 
profiles give the same elevation at Corry crossing and I believe run exactly 
together from Corry to the lake, if they could be compared at precisely the 
same points. They seem both to have been made from one line of levels. 
Where the error in joining the line run from the east with the line run 
from the west may have occurred we do not know,* but certain it is that 
no “‘P. R. R. datum” or ‘‘mid tide Baltimore datum’’ levels have been 
correctly brought through to Irvineton. 
Mr. Gardner in his discussion of R. R. levels to establish the surface ele- 
vation of Lake Erie, says, Lake Erie is above Harrisburg by P. & E. levels 
251’; this added to the height of Harrisburg, 319,75’ = Lake Erie 570.75/. 
If the levels of this road were run from Harrisburg west, and from the Lake 
east, it is perceived at once that the P. & E. levels had nothing whatever to 
do with the difference of elevation between Harrisburg and the Lake. It was 
only the difference between 314’, the starting point at Harrisburg as given by 
Burgin and 565’ the starting point at Erie. The Harrisburg end was raised 
5.75’ to bring it up to correct ocean level, the Lake end 8’ to bring it up to 
accepted lake level, consequently the line showed an error of 2.25 making 
Lake Erie, 570.75/ instead of 573’. Of course it was supposed that the ley- 
els were corrected throughout, but they could not have been correctly con- 
nected in fact, for we shall show that while the western end requires to be 
lifted 11’ the centre needs to be raised from 19/ to 23/. 
We have met this same trouble in other roads in this district, where they 
have been run from one known, or supposed to be known, elevation to an- 
other. They agree at each end with the points given, but our cross checks 
lead to the suspicion that it has required some adjustment and alteration of 
the levels actually obtained to make them do so. 
The re-leveling of the P. & E. R. R. and the corroborative circumstances 
above given should establish the correctness of our Union City adopted ele- 
vation of 1270/ and our Corry adopted elevation of 1427/ at the crossing of 
the P. & E. and A. & G. W. Railways almost beyond a question. They 
cannot vary more than the fraction of a foot from the figures here given. 
They also furnish the data from which to adjust the levels of the O. C. & 
A. R. and Union & Titusville Railways leading from the P. & E. to Oil 
City as will be seen below. 
Absolute accuracy is not of course to be expected in an adjustment of this 
kind, where the levels of different roads are to be tied together and com- 
*It seems quite probable, we think, that the error will be found between West 
Creek Summit near St. Mary’s and Clarion Summit near Kane. In that case 
West Creek Summit should be raised 19’ to correspond with Emporium, and all 
stations between Kane and Warren LI’ to correspond with the Lake end of the 
line. 
