Coal Formatiom; in. the Slate of New York. 25 



It may be proper to add a few remarks upon the probable depth to 

 which borings must be extended, if search is to be made for coal by 

 that method. The only data from which we can deduce probable 

 conclusions, are, the thickness of the strata to be perforated at their 

 bassetting edges. As all the borings would of course be commen- 

 ced on the upper surface of the saliferous rock, the thickness of that 

 rock, of the millstone grit, and of the carboniferous slate, would be 

 the measure of the depth to which the perforations must extend. 

 The thickness of these rocks at their bassetting edges, between Lit- 

 tle Falls and Lake Ontario, is as follows : The thickness of the 

 sahferous rock averages about ninety five feet — that of the millstone 

 grit about forty feet — that of the carboniferous slate about one hun- 

 dred and fifty feet — making in the whole two hundred and eighty five 

 feet. But the sahferous rock increases in thickness throughout its 

 whole extent, from its bassetting edge near Little Falls to the Niaga- 

 ra river. The surface of this rock at Gasport is two hundred and 

 seventy four feet higher than the surface of the waters of Lake On- 

 tario. Here it disappears beneath the waters of that lake ; and from 

 a consideration of its uniform dip, as far as it can be observed, its un- 

 der surface must be at the depth of at least one hundred feet below the 

 surface of the lake. Then allowing forty feet for the thickness of 

 the millstone grit, the upper surface of the carboniferous slate will be 

 four hundred and fourteen feet lower than the surface of the salifer- 

 ous rock at Gasport. If we add one hundred and fifty feet for the 

 thickness of the carboniferous slate rock, the depth of the boring will 

 be five hundred and sixty four feet. It may be stated in round num- 

 bers, that a satisfactory examination, to be made by boring, will re- 

 quire that these rocks be perforated to the depth of six hundred feet. 

 By the same mode of calculation, it appears, that if a similar exam- 

 ination be made at the easternmost locality of native carburetted hy- 

 drogen gas, which is near Vernon village, the perforation must ex- 

 tend to the depth of about two hundred and fifty feet. All the inter- 

 mediate perforations will require to be in proportion to their distances 

 from these two extremes, which are about two hundred miles distant 

 from each other. In Europe, shafts are frequently sunk to the depth 

 of from four hundred to six hundred feet for raising coal from a for- 

 mation equivalent to this. 



There is one locality of native carburetted hydrogen gas, which 

 requires particular consideration. It is in the village of Fredonia, 

 county of Chautauque. Here the gas issues from the upper surface 



Vol. XIX,™No. 1. 4 , 



