THE CARBONIFEKOUS SYSTEM. 



143 



area, the shields of diatoms accumulated in beds of considerable thick- 

 ness, and these, now blended and consolidated by solution, form our Coal 

 Measure buhr-stones. 



In this view, the wide diffusion of the silica and its blending with 

 and shading into purer limestone as though deposited in the quieter 

 nooks of the broad lagoon, its association with fossils and iron, are all 

 harmonious and confirmatory facts. If hot springs had furnished the 

 silica, we should be pretty certain to find it impregnating other strata 

 than the limestone, and should probably find some masses or accumula- 

 tions heaped up about the source of supply but we have discovered 

 nothing of the kind; and the careful observation of the facts in the 

 case has convinced me that the silica, like the lime, is indigenous and 

 not exotic; that is, that it accumulated particle by particle as a sediment 

 at the bottom of water, where it was slowly drawn from solution and fixed 

 by some vital agency. 



Analyses of Coal No. 4. 



No. 1. Sharples's bank, Bedford township, Coshocton county ; cannel... Wormley. 



" 2. Lyman's, Jefferson township, " " 



" 3. Trumbull Company's shaft, Stark county ; bituminous 



" 4. Greentown, Summit county, " 



" 5. Porter's coal, Hopewell township, Muskingum county ; bitum. .. . 



" 6. Flint Bidge cannel 



Coal No. 5. 



In the western part of Holmes county the distance between the Putnam 

 Hill limestone and its underlying coal (No. 4) and Coal No. 6 — to be de- 

 scribed further on — is little more than twenty feet, and no coal seam 

 occurs in the interval. In going toward the east from this point this 

 interval rapidly expands, until in Tuscarawas county it becomes as much 

 as one hundred feet, and one, sometimes two, coal seams are found in it. 



