Geological Survey of the State of Ohio. 355 



glomerate is a few miles west of Jackson, a distance of more than 

 twenty miles east of its termination on the section. Not a ves- 

 tige of it is to be seen in situ, even on the highest hills in the 

 vicinity of Chilicothe. 



We propose to lay before our readers a description of the prin- 

 cipal formations in Ohio, beginning with the oldest rocks and as- 

 cending in the series. 



I. Great Limestone Deposit. — This is the equivalent of the 

 mountain or carboniferous limestone of Europe. It is first struck 

 in Adams county, and extends thence to the western borders of 

 the State. It is of a grayish color, with a tinge of blue, and sub- 

 crystalline in its texture. It generally occurs in layers, varying 

 from a few inches to two feet in thickness, with thin seams of 

 shale intervening. From its toughness, it forms a valuable build- 

 ing material. Organic remains are profusely scattered throughout 

 this deposit. Of Zoophytes, the principal are the Caryophylla, 

 Turhinolia, Cyathophylhim, Favosites, and Astrea. Of the Crus- 

 tacea, Trilohites and Calymene. Of MoUusca, the Spirifer, Pro- 

 ducta, and Terebratula. Of Conchifera, the Melaina, Delphi- 

 niila, Planorbis, Orthoceratites, Ammonites, and Turritella. On 

 some of this limestone we have noticed ripple marks, which were 

 probably contemporaneous with its induration. 



From the appearance of this limestone, it is not unreasonable to 

 suppose that the particles composing it were once held in aqueous 

 solution, and subsequently deposited in tranquil water along the 

 bottom of the ocean. This may have been consolidated by sub- 

 terranean heat, acting on the mass. This is rendered prohahle, 

 by the ingenious experiments of Sir James Hall. From them we 

 derive the -following conclusions : that a compressing force equal 

 to the weight of 53 atmospheres, or 1700 feet of sea, is sufficient 

 for the formation of limestone, if a due degree of heat be applied ; 

 that under 86 atmospheres, or about 3000 feet of water, a com- 

 plete marble may be formed ; and lastly, that, with a pressure of 

 173 atmospheres, or 5700 feet, a little more than a mile of sea, 

 the carbonate of lime is made to undergo complete fusion, and to 

 act powerfully on other earths. These compressions are, com- 

 pai'atively, by no means great. The force of gunpowder, at the 

 least estimate, is equal to the weight of 1000 atmospheres.* 



* Edinburgh Rev. vol. 9, p. 27, Art. Sir James Hall on the Eft'ect? of Ilcat and 

 Compression, 



