May 4, 1877.] 17 [Carll. 
On the results of Surveys in 1876-7 made for the purpose of Rectifying the 
System of Rail Road and Oil Well Levels throughout North West Penn- 
sylvania. 
By J. F. Caruu, AssIsTANT GEOLOGIST IN CHARGE OF THE SURVEY OF 
THE O1L REGIONS. 
(Read before the American Philosophical Society, May 4, 1877.) 
No attempt has heretofore been made to compare and adjust the levels of 
the numerous lines of Rail Roads interlacing the Oil Regions ; consequently 
considerable misapprehension exists, not only as to the true ocean levels, 
but also as to the relative levels of many places frequently quoted and taken 
as points from which to calculate the fall of the surface and streams, or the 
dips of the oil rocks. 
Within this district not one point of elevation has been proven to be cor- 
rect. Harrisburg, Pittsburgh and the surface of Lake Erie are the near- 
est reliable points we have ; and their true heights above mean ocean level 
have only recently been fixed through the well directed and successful 
efforts of Mr. Jas. T. Gardner, Geographer to the United States Geological 
and Geographical Survey of the Territories, under the charge of Dr. F. V. 
Hayden, United States Geologist. 
These elevations above mean surface of the Atlantic Ocean—Harrisburg 
320’, Pittsburgh 745’, and Lake Erie 573’/—are now adopted; and from 
them we propose to carry forward the Rail Road lines of this district, to 
compare their intersections and junctions, and to fix and adopt certain 
points of elevation on which to base our geological work. 
This, perhaps, should have been one of the first tasks of the Survey, but 
the material for it could not at that time have been immediately obtained, 
for even now after working towards the point for three years, much is 
wanting to make the adjustment as complete as could be wished. 
The road most closely connected with the work of this district, is the 
Pittsburgh, Titusville and Buffalo Railway. It passes through the heart 
of the Oil Regions, along the valleys of the Allegheny River and Oil Creek 
from Pittsburgh to Corry and thence over the ‘‘divide’’ to Brockton. Un- 
fortunately, its levels have been very unreliable ; not so much, as we dis- 
cover, now, from inaccuracy in the original instrumental work, as from a 
want of care in adjusting the datum planes of the several roads composing 
the present continuous line, to ocean level. 
The elevation of Oil City, based on these levels has been variously given 
from 995’ to 1049’ above tide.* Other places along the line have varied 
in the same manner, but not to so great a degree.{| There was also a want 
of agreement with the railways intersecting it, at the West Pennsylvania 
*Meaning mean high tide at Philadelphia, Pennsylvania Rail Road datum ; 
mean tide at Baltimore; mean tide at New York (Via Lake Erie), &c. 
+ Except at points like Driftwood on the Philadelphia and Erie Rail Road, 
PROC. AMER. PHILOS. Soc. xvi. 100. ¢ 
