1865.] 43 [Lesley. 



in cuttino; down their canons to the bottom of the sand mass, 

 so as to aflford an exit for that proportion of the petroleum 

 which had there collected to begin its escape ; how far the 

 petroleum, in its downward progress, has passed through the 

 ore and coal-shales, and has found still lower horizons to stop 

 it, and is there waiting for the oil-well borers to come and 

 give it issues to the surface; and to what extent, on the other 

 hand, the deeper and older petroleums (of which I shall speak 

 hereafter) have found fissures from below, up which to as- 

 cend to mingle with this petroleum of No. XII : these are 

 questions of the greatest practical importance, which no one, 

 so far as I know, has distinctly stated; and they can only be 

 fully answered after long practical investigation. 



A Conglomerate age or horizon of petroleum exists : this is 

 the mai'n point to be stated. It must be kept in view apart 

 from all other ages or horizons of oil, whether later or earlier 

 in order of geoloo-ical time. I have no doubt that some of 

 the petroleum flowing or pumped from old salt wells in South- 

 western Pennsylvania comes from this horizon of No. XII. 

 The rock itself is full of the remains of plants, from the de- 

 composition of which the oil seems to have been made. I 

 noticed in the great rock pavement, at the Lyon's Well, over 

 which the creek water flows, many sections of tree branches 

 and stems, mashed flat, each section being, say 6 inches long 

 by ^ inch wide in the middle ; and when a jack-knife was thrust 

 down into the slit, so as to clear it of mud, the black tarry 

 oil would immediately exude and spread itself over the water. 

 A pointed hammer spalling ofi" flakes of the rock on each side, 

 shoAved not only that the slit itself was full of thick oil, but 

 that the whole rock was soaked with it, except along certain 

 belts (an inch or less wide and very irregular), Avhich, for some 

 unexplained reason, remained free from the oil.* Similar 

 specimens of "oil-rock" were obtained in other parts of the 

 valley, and may be got almost anywhere. Mr. Lyon was so 

 much impressed with the quantity of petroleum thus held per- 

 manently by the sandrock itself, apart from the immediate 



• * My specimens still show this very remarkable peculiarity, although 

 I have had them in a dry, warm room for weeks. 



