44 W. D. KELLER 
LIMESTONE 
The resistivity of the Kimmswick limestone is shown on Graph 
No. 5 under three different conditions. First, curve 77, the limestone 
with no soil cover, was measured where it was cleanly exposed in the 

bed of a small creek one mile north of Elsberry, Lincoln County. The 
electrodes were laid directly on the limestone in the shallow, almost 
quiet water of the stream. 
The next set-up, 76, was made about 35 feet north of 77, where the 
same limestone was covered by about 3 feet of alluvium. The resistiv- 
ity here is uniformly about 30 units less than that of 77. The writer 
566 
