Briggs.l IIQ [May 19 



the whole arrangement being used also for farming purposes, to serve 

 as common field fences. 



Mr. Lesley agreed with Mr. Briggs as to the total absence of all 

 practical surface indications of a strictly local kind, available in even 

 the slightest degree for[^determining the position of any well ; and 

 also in the opinion which Mr. Briggs expressed that the upland is as 

 good oil-boring territory as the valley bottoms, the necessary addition 

 to the depth of the well being of no practical importance. 



He described and objected to such sections of the valley as that 

 recently published in the Oil Region Atlas, and to the whole theory 

 of valley-bed subsidence, faulty structure of the foot of the valley- 

 walls, disturbed condition of oil regions, and other popular notions 

 of surface disorder, considered as indications of the goodness of 

 boring localities. He referred to the privately expressed opinion of 

 a distinguished geologist, that the petroleum was pressed towards the 

 valleys by the weight of the upland on each side, where the action 

 had cracked the valley bed in the style of a floor-creep in a coal 

 drift, and showed that it was improbable on the mechanical theory 

 of the reversed arch. 



He described the three great conditions for oil; first, an abundance 

 of organic remains; secondly, a permeable and yet compact sandy or 

 gravelly horizontal oil reservoir; and thirdly, a system of vertical oil 

 reservoirs or open cleavage-planes, in polar directions, but confined 

 to single formations, and having nothing whatever in common with 

 the great faults which penetrate the earth crust in disturbed districts. 

 He concluded that the general geological characteristics of an oil re- 

 gion were as fixed and reliable as the local surface indications were 

 the contrary. He took the liberty of describing the yet little under- 

 stood theory of M. Lesquereux (who had been prevented by circum- 

 stances from sending a memoir on the subject, to be read at this 

 meeting), consisting essentially in the distinction between the genesis 

 of coal from woody fibre, and the genesis of petroleum from non- 

 fibrous vegetation, or marine fucus ; and said that the Society might 

 hope soon to have the explanation of this generalization in all its 

 bearings from the eminent botanist who has done so much for the 

 elucidation of the geology of the coal measures. 



Mr. Chase described his lute visit to some wells in Southern Penn- 

 sylvania, and showed how ignorantly the popular notion of three 

 sandrocks was carried from the Venango to other and distant regions, 

 and applied absurdly to a difi"erent geological condition of things. 



