12 The Ohio Journal of Science [Vol. XVIII, No. 1, 



were the ledges arched and the space filled in? Or are the 

 forms contemporaneous with their surrounding strata? Why 

 out of the six forms only two are frequently found in other 

 exposures of the same limestone in the same locality? 



The "cup and cone" concretions with their cavities often 

 filled with rock pieces crushed in, suggest pressure as a cause. 

 But then why are they not found in the lower Gray Stone where 

 pressure would be greatest? Why do they occur most frequently 

 in a few ledges near the middle of the exposure? Always being 

 vertical, seldom inclined and never horizontal, has this definite 

 position any importance? The lithological differences between 

 the Gray and Buff stones, have they any bearing on the prob- 

 lems involved? These important questions I desire to submit 

 for further, careful consideration. 



CORRELATION. 



I have found specimens which are suggestive that there 

 may be a relationship between these and other concretionary 

 forms. If this can be sustained, then we have made quite an 

 advance towards the explanation of the common force which has 

 operated, what it is and how it has operated. 



At the center of an unbrecciated, unfossiliferous isolith 

 which had been bisected, I found a large mass of sphalerite, 

 well crystallized and weighing thirty (30) pounds. Its position 

 was suggestive that it had been the nucleus of the isolith' s 

 aggregation, a striking similarity to where concretions are 

 formed with fish bones, leaves, etc., as nuclei. 



Embedded in a fossiliferous, unbrecciated isolith I have 

 found concretionary "pebbles" with characteristic ring around 

 ring structure in cross section. This seemingly joins my lowest 

 and next to highest forms as the result of a common force. 



The stem of the "cup and cone" concretion sometimes 

 has a structure somewhat similar to the "cone in cone" form. 

 As pressure is now regarded the probable cause of the latter, 

 any relationship that can be established with the former is 

 evidence of some corroborative character for the pressure 

 theory. The crushed-in particles in the cavity are ever strongly 

 suggestive of pressure. 



In the disturbed ledges near the contact with the isolith, 

 I have found smoothed, grooved portions. This is evidence 



