308 GEOLOGY OF OHIO. 



A satisfactory measurement of the thickness of the Huron shales could 

 not be obtairiiedin the county ; but from the reported boring for water in 

 the machine shops in Norwalk, I estimate it at not less than seven hun- 

 dred feet above the top of the nearest exposure of the Cleveland shale. The 

 tubing was driven at the machine shops ninety-nine feet through sand 

 and clay before striking rock. The well was sunk to a depth of eight hun- 

 dred feet from the surface without reaching limestone, and " most of 

 the way in black shale." Near the bottom, a plentiful supply of clear 

 sparkling water was obtained, but having an offensive odor. Thid is 

 characteristic of all the water in the county which percolates through 

 these shales, and I presume that from the Norwalk well was obtained 

 from the bottom of the formation. Deducting one hundred feet for the 

 aggregate thickness of the Cleveland and Erie shales, which is certainly 

 enough, we have seven hundred and fifteen feet as the thickness of the 

 Huron. This is much greater than the reported thickness, but is not too 

 great, unless there is an error in the reports of the well-boring. I regret 

 that no written record was kept of the drilling. 



Since the field-work of the county was completed, specimens of so- 

 called coal found in these shales have been S3nt me for examination. 

 They consist of flat pieces of carbonaceous matter minutely fissured, and 

 the fissures filled with thin plates of sulphate of Baryta. The nature 

 and origin of these deposits are easily understood. The Huron shale is 

 the great oil producing rock of eastern Ohio and western Pennsylvania. 

 The slow distribution of the bituminous matter in it has resulted in the 

 production of gas and petroleum, which along the outcrop of the strata 

 have steadily escaped. The petroleum flowing into a fissure in the rocks 

 where it was retained, has parted with its volatile matter, leaving a 

 residuum of asphaltum or Albertite which by continued desiccation has 

 become minutely cracked and the fissures have been gradually filled 

 with barite. Such deposits afford no proof that "the geologists have 

 been mistaken," and no encouragement whatever to the hope that a 

 valuable deposit of coal may be found outside of the " Coal Measures." 

 True coal in very thin laminae is occasionally found in this shale, and in 

 all the formations between it and the Coal Measures, land plants seem 

 to have flourished under favorable conditions during the time of the 

 deposit of all the upper Devonian, and the sub-carboniferous rockB. 

 It has left its record in plant impressions, and in isolated thin films 

 of coal which may be found on almost any horizon of these rocks ; but if 

 taken as indications of the presence of workable deposits of coal, they 

 will unquestionably lead to disappointment. 



