GENERAL GEOLOGY OF CLAYSVILLE QUADRANGLE. 
55 
for each 5 feet of vertical change on a straight line connecting the 
wells. The isochor lines (curved lines on the drawing) are supposed 
to be drawn through points of equal distance between the beds. It 
can be readily seen, however, that in this wav no account is taken of 
changes in the rate of convergence that may exist over local areas 
between wells, and that it is possible to refine the drawing indefinitely 
as new measurements between the beds are introduced. At several 
places in this quadrangle the evidence of a change in the rate of con¬ 
vergence between wells has been considered sufficiently strong to 
warrant the drawing of the isochor lines so as to cross the straight 
lines connecting wells at points other than those obtained by propor¬ 
tioning the distance. The most notable deviation of this kind from 
the regular method of making up the drawing is over a large portion 
of the lower right-hand corner. By placing the transparent con¬ 
vergence sheet over the map of the oil sand (PI. XIII) it will be 
seen that a broad belt of very rapid convergence is shown to pass 
through the southern part of South Franklin, the northwest corner 
of Morris, and the southeastern part of East Finley townships. Evi¬ 
dence showing the existence of this rapid change in distance between 
the beds in the southern portion of the belt is presented by wells Xos. 
956 and 948. In No. 956 the J. II. Irwin well No. 1, on Rocky Run, 
1 mile west of the village of Gale, the distance between the Upper 
Washington limestone and the Gordon sand is 2,710 feet. In the 
Ben Farabee well (No. 948), 1 mile north of Old Concord, the dis¬ 
tance, though not accurately determined, is about 2,805 feet, showing 
a change of 95 feet in the interval between these beds. On the con¬ 
vergence sheet this change is represented as occurring uniformly 
between the wells, but it is possible that the rate varies considerably, 
though there is no way of determining at what place these variations 
occur. From the Farabee well above mentioned to well No. 947, on 
the Lee Andrews farm one-half mile north of Lindleys Mill, the 
distance between the Upper Washington limestone and the Gordon 
sand increases onlv 20 feet. This increase, it should be noticed, is 
not distributed proportionately between the wells, and it is possible 
that the change in the rate of convergence just east of the Farabee 
well is even less abrupt than that shown by the isochor lines. Unfor¬ 
tunately, the J. L. ITogue well (No. 946), three-fourths of a mile 
east of Old Concord, did not reach the Gordon sand, and of the wells 
of Greene County a short distance south of this quadrangle none 
afford a good measurement between the Upper Washington limestone 
and the Gordon sand, so the isochor lines in that vicinity are drawn 
more or less hypothetically. At well No. 951, the B. C. McCarroll 
well No. 1 on Crafts Run, the distance between these beds is 2,780 
feet, which shows a change of 70 feet between this well and the 
