288 ANNUAL OF SCIENTIFIC DISCOVERY. 



but in Canada, from the absence of this substance, diffused through 

 the shales in question, we are forced to assign it to a lower horizon, 

 which is doubtless tbat of the bituminous Devonian limestone. 



The question of the extent of the supply of petroleum is not easily 

 answered ; the oil now being wrought is the accumulated draining 



d> C2 Cj 



of ages, concentrated along certain lines of elevation, and the expe- 

 rience of other regions has shown that these sources arc sooner or 

 later exhausted ; but though the springs of Agrigentmn, like those 

 of Derbyshire, have nearly ceased to flow, those of Burmah and Per- 

 sia still furnish, as they have for ages past, immense quantities of 

 oil. Nothing but experience can tell us the richness of the subter- 



ranean reservoirs. 1 



Professor Newbeny, the well-known geologist, in a recent pam- 

 phlet on the Rock Oils of Ohio, presents the following explanation of 

 the origin of petroleum : 



Petroleum has usually been produced from bituminized plants, but 

 those varieties of it which are obtained from rocks filled with animal 

 remains, as highly fossiliferous limestones, and which have a pecu- 

 liarly strong and disagreeable odor, in virtue of the sulphur and ni- 

 trogen which they contain, are probably for the most part of animal 

 origin. 



The precise process by which petroleum is evolved from the car- 

 bonaceous matters contained in the rocks which furnish it, is not yet 

 fully known, because we cannot in ordinary circumstances inspect it. 

 We may fairly infer, however, that it is a distillation, though gener- 

 ally performed at a low temperature. Carburetted hydrogen is rap- 

 idly produced from bituminous substances by artificial dry distillation. 

 So it is evolved in nature, at low temperatures, from submerged, and 

 doubtless emerged, vegetable matter. It is also thrown off in im- 

 mense quantities by the spontaneous distillation of bituminous coal 

 in mines. Doubtless the same is true of the liquid hydro-carbons. 

 Though less observable than the gases, I think they may often, if not 

 always, be detected among the products of decomposition of sub- 

 merged vegetable tissue. This at least we may safely affirm, that 

 their spontaneous production on a large scale in nature may gener- 

 ally be traced to extensive accumulations of bituminized vegetation 

 from which they have been derived. From this they are evolved 

 by a kind of distillation, which differs from our artificial process in 



lercat depths, as has been already shown, consequently there is no such thing- as 

 an ' oil rock,' as many suppose. The oil is found in any kind of stratum. Each 

 oil fissure doubtless extends vertically, or nearly so. through many different strata. 

 These wells have been unparalleled i'or the quantity of oil produced. Many of 

 them, when first bored, poured out the oil in torrents, the oil being forced up by 

 the pressure of gas. Hundreds of barrels were obtained from a well in a few 

 hours. 



" The oil is evidently the accumulation of long ages. The valleys of erosion 

 which cross this line of uplift in almost every direction, and which have been 

 produced by the drainage of the rains falling upon the surface, show that the up- 

 lift, and consequently the fissures underneath, have existed for a vast period of 

 time. It is therefore probable that during this long period the work of accumu- 

 lation has been going on. If this is true, it will follow that when a fissure is once 

 exhausted of oil, it may well be abandoned, as it will take a geological period to 

 refill it." 



