lis THE CANADIAN NATURALIST. [March 



except in tlie case of the rare limestone beds ah-eady referred to, 

 which are occasionally iuterstratified . Iteservoirs of petroleum 

 are met with, both in the overlying quaternary gravels and in the 

 fissures and cavities of the Hamilton shales, but in some cases the 

 borings are carried entirely through these strata, into the Corni- 

 ferous limestone, before getting oil. Among other instances cited 

 in my Geological Report for 1866, may be mentioned a well at 

 Oil Springs, in Enniskillen, which was sunk to a depth of 456 

 feet from the surfoce, and seventy feet in the solid limestone 

 beneath the Hamilton shales, before meeting oil, while in adjacent 

 wells supplies of petroleum are generally met with at varying 

 depths in the shales. In a well at Bothwell, oil was first met 

 with at 420 feet from the surface, and 120 feet in the Corniferous 

 limestone, while a boring at Thamesville was carried 332 feet, of 

 which the last thirty-two feet were in the Corniferous limestone. 

 This well yielded no oil, until, at a depth of sixteen feet in this 

 rock, a fissure was encountered, from which, at the time of my 

 visit, thirty barrels of petroleum had been extracted. At Chat- 

 ham, in like manner, after sinking through 294 feet of shales, oil 

 was met with at a depth of fifty-eight feet in the underlying 

 Corniferous limestone. 



We also find oil-producing wells sunk in districts where the 

 Hamilton shale is entirely wanting, as in Maidstone, on the shore 

 of Lake St. Clair, where, beneath 109 feet of clay, a boring was 

 carried through 209 feet of limestone, of which the greater part 

 consisted of the Water-lime beds of the Salina formation, overlaid 

 by a portion of the Corniferous. At a distance of six feet in the 

 rock a fissure was struck, yielding several barrels of petroleum. 

 Again at Tilsonburg, where the Corniferous limestone is covered 

 only by quaternary clays, natural oil springs are frequent, and, 

 by boring, fissures yielding petroleum were found at various 

 depths in the limestone, down to 100 feet, at which point a flow- 

 iup- weir was obtained, yielding an abundance of water, with some 

 forty gallons of oil daily. The supplies of oil from wells in the 

 Corniferous limestone are less abundant than those in the over- 

 lying shales, and even in the quaternary gravels, for the obvious 

 reason that both of these offer conditions favorable to the reten- 

 tion and accumulation of tlie petroleum escaping from the 

 limestones beneath. 



The presence of petroleum in the Lower Silurian limestones, 

 and their probable importance as sources of petroleum, was first 



