GEOLOGY. 253 



natnral-jjas vents were known to and were for ages venerated by the 

 lire- worshipers, wliose cult tbey inspired ; it is also true that springs 

 of mineral oil Tiave been known from history's dawn, and tliat the oil 

 was utilized sometimes as fuel or ilhiminant, though more commonly 

 as a medicine or lubricant ; and it is equally true that natural oils and 

 tars were extracted by primitive means and used for primitive pur- 

 poses by barbarous Oriental peoples long before their fame spread to 

 the Occident; but it is only within a few years that these natural 

 products have been utilized so extensively as to materially modify the 

 course of human progress. 



Fa)i2)assu with the industrial development accompanying the utili- 

 zation of rock gas, geologic science made an unparalleled stride within 

 a few months. During the last thirty years Hunt, ISewberry, Peck- 

 ham, I;eslie, and several other geologists in this country, and Biuney, 

 Coquand, Daubree, Lartet, and others abroad have indeed made im- 

 portant contributions to our knowledge concerning the constitution and 

 origin of petrolenm and its associates; and the exploitation of the 

 Pennsylvania-New York fields afforded valuable additional data relat- 

 ing to these minerals. Nearly four years ago Prof. I. C. White enun- 

 ciated and vigorously maintained the theory — now recognized as a 

 fundamental law in gas prognostication — that gas, oil, and brine are 

 accumulated in the order of their weight within inverted basins and 

 troughs formed by flexure of the rocky strata. The importance of 

 these contributions to our knowledge of the lighter bitumens must not 

 be under-estimated; yet when exploitation for gas began in Ohio in 

 188G, the geologist literally sat at the feec of the prospecter gathering 

 such crumbs as fell from his hands, and found himself utterly unable 

 either to guide eitbrts or predict results. Less than two years later the 

 laws governing the distribution and accumulation of gas and oil were 

 80 fully developed that the rock-gas problem claimed a solution as sat- 

 isfactory as that of the well-known artesian water problem ; andtoday 

 the geologist predicts the success or failure of a prospect bore for gas 

 or oil about as readily and reliably as he can prognosticate artesian 

 water, or coal. Greater advance was probably never before made in so 

 limited time in any economically important branch of knowledge. The 

 solution of the ])roblem of rock gas and petroleum marks an era iu 

 science no less than in industry. Vast sums of money, reaching some- 

 times into the millions, were spent by prospecters in gathering data; 

 but the credit for the solution of the problem belongs chiefly to three 

 individuals— I. C. White, of the University of AVest Virginia; Edward 

 Orton, State geologist of Ohio; and A. J. Phinney, a practicing physi- 

 cian and amateur geologist of Muncie, Indiana. 



GLACIATION. 



The general tcMidency of glaciation is to obliterate surface irregularity 

 both by grinding down elevations and by filling uj) depressions, and 

 thus to sui)plement hydric gradation ; but glaciation may also acceut- 



