248 BITUMINOUS COAL STRATA. 



were strong currents of water, depositing only 

 coarse sand and pebbles ; in this the waters were 

 ^ less disturbed, and often tranquil, and so varied and 

 charged with materials as to produce layers of 

 sandstone, limestone, shell, coal, and iron ore ; thus 

 forming a series of strata some hundred feet in 

 .thickness, containing rich suppUes of the most use- 

 ful substances for the necessities and comforts of 

 man. During this period must have flourished ex- 

 tensive, forests of terrestrial plants, as we find their 

 remains scattered with great profusion through the 

 whole of this series of strata. 



VI. The next division (G) is a rock only a few 

 feet in thickness, but so remarkable in its charac- 

 ter, so continuous, and requiring conditions for its 

 promotion so widely different ifrom those of any 

 other rocks in the state, that it deserves special at- 

 tention. This rock has been called huhr, from its 

 strong resemblance to the buhrstone of the Paris 

 Basin, and its use in the construction of millstones, 

 to which both have been applied. This rock is 

 chiefly composed of silex, but it occasionally con- 

 tains some calcareous matter. Unlike others of 

 which we have spoken, it seems to have been a 

 deposition from waters containing the materials in 

 chemical solution. It is characterized by the re- 

 mains of molluscous animals. 



VII. This division (H) includes the series of strata 

 above the buhr. It consists of alternations of sand- 

 stone, limestone, shale, coal, and iron ore, and may 

 be considered the upper member of the coal forma- 

 tion. 



Dr. Hildreth, in his late report on the Geology of 

 Ohio, has given a section of 35 distinct strata, which 

 lie above the calcareo-siliceous rock marked G in 

 the above cut, consisting of sandstones, shales, 

 limestones, clays, iron ore, and four beds of coal, 

 altogether amounting to a thickness of over 600 feet. 



