'220 .'Professor J. Jolij—The Age of the Earth. 



But I may be allowed to remark that tlieir exorcism comes rather 

 •late iu the day. Such an investigation ought to have been under- 

 taken at least a dozen years ago, that is to say, before the specimen 

 was displayed in the principal musemii at Berne, figured and 

 described by a government department, and trumpeted forth to the 

 world by an official geologist as a discovery of prime importance in 

 the history of metamorphic rocks. For twelve 3'ears this error has 

 been infecting textbooks and impeding progress ; but at last the 

 phint - remains in the gneiss of Guttannen have gone to join 

 the schists, where garnets and staurolites dwell in unity with 

 belemnites, in that limbo which is appointed for exploded hypotheses. 

 Mequiescant in pace I 



IV. — The Gkologtcal Age of the Earth. 



By J. JoLY, M.A., D.Sc, F.R.S. 



fl^HE able review of my paper on the Geological Age of the Earth 



which appears in the March number of this Magazine (p. 124), 

 from the pen of the Eev. 0. Fisher, raises again questions of such 

 wide interest that some further remarks, referring principally to 

 the criticism of the distinguished writer of the review, and also 

 to criticisms which I have received from others and which are 

 probably in the minds of many who have considered the matter, 

 may not be out of place. 



My position in reference to the mode of estimating the Geological 

 Age of the Earth advocated in my paper has, of course, been that 

 of the Uniform itarian. In answer to general objections on this 

 score, I have only to say that •positive knowledge on the subject 

 under discussion will probably never be attained by Science. 

 Kecognizing this, we may ask of the Physicist on the one hand, 

 and of the Geologist on the other, to what the probable error- 

 limits of their several methods of computation may amount. Will 

 the Geologist admit as probable, denudative activities continued 

 throughout the entire past of geological history which are sufficiently 

 discordant with those of to-daj'^ as to bring his error-limit to the 

 magnitude of that confessed to by the Physicist ? Will he admit, 

 in short, that the activities of to-day may have been five times 

 excelled or five times diminished, and stand divided between the 

 possibility that they were maintained at the one or the other of these 

 magnitudes throughout geological time ? In other words, that our 

 hundred million years may have been five hundred millions or twenty 

 millions so far as denudative processes can tell us ? Yet it is just 

 this position the Geologist must assent to before he attains to 

 the uncertainty which divides Physicists on this question at the 

 present day. I need not draw the obvious inference or review 

 the question further. 



Among geological methods, that one which I have advocated 

 (and in which I was in part anticipated by Mr. Mellard Eeade) 

 claims, as I have contended, the safest and most restricted measure 

 of Uniformitarianism — claims, in fact, uniformity confined more 



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