GEOLOGY. 289 



wanting, in many cases at least, the condition of high temperature, 

 but including the perhaps no less potent elements of time and pres- 

 sure. 



Production of Petroleum. The amount of petroleum (rock oil) 

 daily drawn from wells bored to obtain it in the States of Pennsyl- 

 vania and Ohio was estimated by Prof. Newberry, for 1860-61, to be 

 not less than live hundred barrels, or over five million gallons yearly. 

 The amount of rock oil which passed over one of the Pennsylvania 

 railroads the Erie and Philadelphia during the month of Jan- 

 uary, 1862, ig reported to have been thirty thousand barrels. Oil 

 in large quantities is also obtained in Canada and Kentucky ; and 

 its collection, transportation, refining and vending has, in all the 

 above-mentioned localities, given a prodigious impulse to enterprise 

 and industry, giving employment to thousands, trebling the popula- 

 tion of some towns, starting others into existence, and causing the 

 construction even of lines of railroads. In fact, there is probably no 

 business in the w r orld which has grown to such magnitude in so brief 

 a period. 



PRODUCTION OF THE CRYSTALLINE LIMESTONES. 



In most modern treatises on geology an experiment, made by Sir 

 James Hall in 1804, of subjecting chalk, contained in a tight gun- 

 barrel, to an intense heat, is quoted as explanatory of the origin of 

 the crystalline limestones or marbles. Experiments of the same 

 nature made during the past year by Rose, show, however, that 

 chalk or compact limestone cannot be converted into crystalline lime- 

 stone by exposure to a high temperature in closed vessels ; and that 

 the conclusions of Mr. Hall, so often quoted, were erroneous, and 

 probably founded on a hasty and imperfect examination of the 

 results he obtained. It is not however, says M. Rose, to be disputed 

 that at the junction with granite and basalt, compact limestone and 

 chalk are often converted into marble, but these changes cannot be 

 considered as due to heat alone ; they were manifestly assisted by 

 other agencies. Silliman's Journal, July, 1861. 



ORIGIN OF THE WESTERN PRAIRIES. 



M. Leo Lesquereux, the well-known geologist, who has carefully 

 studied the prairies of the Mississippi valley, ascribes their general 

 formation to the agency of water. He say;- : 



All the prairies still in a state of formation along the great lakes 

 of the north are nothing else but marshes slowly passing to dry 

 land by slow recession of water. When land is continually cov- 

 ered by low stagnant water, its only vegetation is that of the rushes 

 and of the sedges. When the same land is alternately subjected to 

 long inundations and then to dryness, during some months of the 

 year, the same plants continue to cover it. By their decomposition 

 these marshy plants produce a peculiar ground, either black, light, 

 permeable when it is mixed with sand, as it is near the borders of 

 the lakes, or hard, cold, impermeable when it is mixed with clay or 

 muddy alluvium, as in some marshes underlaid by clay or shales^ or 

 alon"- the banks of some rivers. Land continually covered with 



o 



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