302 



GEOLOGIC TIME. 



numerous observers, and the literature of geology was enlarged by con- 

 tributions dealing with nearly every phase of the subject. 



Hiitton. — Dr. James Hutton was the founder of physical geology and 

 the predecessor of Lyell in advocating the uniformitarian theory of 

 geology. It is, iu a great measure, true — as Lyell has well said of Hut- 

 ton's attempt to give fixed principles to geology — that " too little prog- 

 ress has been made toward furnishing the necessary data to enable 

 any philosopher, howev^er great h is genius, to realize so noble a project." * 

 In his first memoir Hutton t speaks of a method of measuring the dura- 

 tion of geologic time as follows: 



"We are investigating the age of the present earth, from the begin- 

 ning of that body, which was in the bottom of the sea, to the perfection 

 of its nature, whicli we consider as in the moment of our existence; and 

 we have necessarily another era, which is collateral, or correspondent, 

 in the progress of those natural events. This is the time required, in 

 the natural operations of this globe, for the destruction of a former 

 earth, an earth equally perfect with the present and an earth equally 

 productive of growing plants and living animals. Xow, it must appear 

 that if we had a measure for one of those corresponding operations we 

 would have an efjual knowledge of the other. 



* 



* 



* 



"The highest mountain may be levelled with the plain fi'om whence 

 it springs without the loss of real territory in the land; but when the 

 ocean makes encroachment on the basis of our earth, the mountain, 

 unsupported, tumbles with its weight; and with that accession of hard 

 bodies, moviible with the agitation of the waves, gives to the sea the 

 power of undermining farther and farther into the solid basis of our 

 land. This is the operation which is to be measured; this is the mean 

 proportional by whicli we are to estimate the age of worlds that have 

 terminated, and the duration of those that are but beginning." 



He then discusses the data for estimating the length of time it has 

 taken for a specific amount of erosion, and concludes "that all the 

 coasts of the present continents are wasted by the sea, and constantly 

 wearing away upon the whole; but this operation is so extremely slow 

 that we cannot find a measure of the quantity in order to form an esti- 

 mate. Therefore, the present constituents of earth, which we consider 

 as in a state of perfection, would, in the natural operations of the 

 globe, require a time indefinite for their destruction." 



He believed that the continents thus destroyed were formed from the 

 ruins of pre-existing continents, and that there were records of three 

 such ijeriods, each of which, in our measurement of time, were of indefi- 

 nite duration. I 



LycU.—lu 1830 Sir Charles Lyell began to publish the results of his 

 profound and philosophical studies of geologic phenomena. He firmly 

 established the broad outlines of the law of uniformity as opposed to 



* FrincipUs of GeoUgy, 12th Ed., 1875, vol. i, p. 73. 



tTbeory of the Earth; or an Investigation of the Laws Observable iu the Compo- 

 sition, Dissolution, and Restoration of Laud upon the Globe. Trans. Hoy. Soc. Edin- 

 burgh, 1788, vol. I, pp. 297, 298. 



tLoc. cit., p. 304. 



