•detenniiit- tlie iliftVreuc*' in level between the two points. For ussistance in this 

 ■work I am indebted to Mr. C. E. Siebenthal ;ind Mr. George Champ. The dis- 

 tance between tlie two i>oiiits was estimated by stadia measurement. A reduction 

 •of the data obtained showed the points to be 1] miles apart, and the dip of strata 

 between them to be at the rate of 60.6 feet to the mile. This result was so much 

 larger than was anticij)atcd that the ground was gone over a second time by Mr. 

 'Cham|i and myself. The second survey, with a "Y" level, confirmed the cor- 

 rectness of the (irst, thus showing the Keokuk strata to have a diji west of nearlv 

 <i4 feet to the mile in the neighborhootl of Bloomington. 



Wavk Marks on Cincinnati Limestone. By. W. P. Shannon. 



In the southwest part of Franklin County, three miles west of Oldenberg, in 

 the bed of Salt Creek, are good examples of wave marks on Cincinnati limestones. 

 These wave marks are nothing new. They have been referred to by different 

 students of the Cincinnati strata, and are characteristic, since they occur at all 

 horizons of the Cincinnati rocks. This does not signify that every stratum or layer 

 is so marked, but that such marks are rarely found in other than the Cincinnati 

 limestones. Another stratigraphic character of the Cincinnati rocks is the alterna- 

 tion of strata of limestone and shale. The strata are thin, each one being usually 

 made of a single layer or ledge. 



Within a distance of one-quarter mile up and down the bed of the creek, four 

 wave-marked strata are exposed, and according to the law of the Cincinnati forma- 

 tion, each one is overlaid by a stratum of shale. Of these four wave-marked 

 -strata the three uppermost are consecutive, not consecutive strata, but consecutive 

 limestone strata. 



In no two strata are the wave marks in the same direction or of the same size. 

 All four of these strata are fine grained, compact limestone, showing that they 

 were made of calcareous sand or mud. A description of two of these wave-marked 

 strata will be suHicient, the two which have the greatest exposure. One forms an 

 uninterrupted floor to the stream for a distance of 100 feet; the width of this floor 

 is 25 feet. The wave marks are transverse to the course of the stream, and if we 

 stand at the lower end of this area and look up stream it is hard to keep from 

 thinking that we are looking at real undulations in water. It reiiuiresa conscious 

 ^fl'ort to keep from identifying the efl'ect with the cause. If we measure these 

 Avaves, they are about two feet from crest to crest, with a vertical distance of about 

 ihree inches from crest to hollow. Besides wave marks this ledge shows mud 



