GEOLOGICAL AND NATURAL HISTORY SURVEYS. 4o5 



John Sheafer, E. Desor, Leo Lesqiiereiix, J. P. Lesley, A. A. Dalson, 

 W. B. Eoger.s, jr., and Mr. Poole, and published the Geology of 

 Pennsylvania in 1858, as already noted. 



In the interval of 13 years betAveen 1841, when the first survey 

 stopped, and 1854, when all oiRcial field work practically ceased, a 

 great development of the coal and iron industries of the State took 

 place. Hundreds of mines had been opened; many new mineral dis- 

 tricts had been prospected and more or less occupied; railroad cut- 

 tings had exposed a multitude of measurable outcrops; the state- 

 ments of the Hrst survey liad been criticized and verified, and a large 

 body of fresh data added. 



In the next interval of 20 years, between 1854 and 1874, a far 

 greater change took place. The discovery of rock oil in 1859 con- 

 verted in a few years the silent forests of northwestern Pennsylvania 

 into an open region, crowded with villages, towns, and cities, ani- 

 mated with a geological fury for investigation, and penetrated to a 

 depth of 2,000 feet by many thousand bore holes ; so that no part of 

 the earth's crust ever was or is ever likely to be again so completely 

 and minutely explored; nor was ever so \'ast an accumulation of 

 stratigrapliical data thrown together in a heap at the feet of the 

 science. 



Then came the war of secession and an unprecedented demand for 

 iron, and for coal to smelt iron. One-half the annual product of 

 both iron and coal in the United States has always come from Penn- 

 sylvania. Abandoned mines were reworked, new ones opened, fur- 

 naces enlarged, collieries deepened and extended. Every outcrop of 

 iron ore, good and bad alike, was traced and tried; every outcrop of 

 black slate exposed to eager inquisition. A multitude of private 

 surveys took place in all parts of the State, and a world of fresh 

 data, of a specially precise kind, was accumulated, which appealed to 

 a largely increased geological intelligence in the public mind. 



The invention of Bessemer iron when introduced into Pennsylva- 

 nia in 18G7 not only intensified the critical search for ore, but multi- 

 plied the number and imjjroved the quality of metallurgical experts, 

 and thus exercised an important influence upon the sentiment of the 

 (Jonnnonwealth toward geology as an applied science. There was a 

 continually louder call for geological facts. But there was no State 

 bureau of geology nor any officer of the Connnonwealth from whom 

 !-;Uch could be obtained. All surveys were private; all reports confi- 

 dential. Business refused to give away its valuable secrets. The 

 publications of the first State survey were out of print and out of 

 date; would net answer cjuestions if they could, and could not if they 

 would; for the lifetime of a generation had elapsed and a new survey 

 of the State vras needed, under better ausi)ices and with vastly greater 



