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



These isoliths have 8 x 10 x 12 feet as average dimensions 

 and appear as large ovals. They are a hindrance to quarrying, 

 being difficult to break up and causing uneveness in adjacent 

 ledges. Operations downward usually cease when they are 

 reached. 



The first isoliths studied were of solid texture and not 

 fossiliferous, and I was then disposed to regard them as a form 

 separate and distinct from the brecciation well known as occurring 



Fig. 1. An Isolith. Curving Strata Clearly Shown. 



in the Monroe formation, of which the Greenfield Limestone 

 is the basal member. But later finding isoliths of brecciated 

 structure and fossilferous, and unable to observe the resumption 

 of stratification beneath, I am now rather of the opinion that 

 both forms, to some degree, are manifestations of the same 

 force of aggregation. Why then I continue to mention isoliths 

 among concretionary forms, will appear in the correlation I 

 shall present further on in this paper. 



Isoliths afford us two interesting features — ledges can often 

 be traced through them and come out on the other side — they 

 sometime contain a fauna not characteristic of the immediately 

 surrounding ledges. 



