458 Notices of Memoirs — British Association — 



The limits within which the physicist wouhl circumscribe the earth's 

 history was so vague, yet so vast, that whether the time allowed 

 were 400 millions or 100 millions of years did not seem to them 

 greatly to matter. After all, it was not the time that chiefly 

 interested them, but the grand succession of events which the time 

 had witnessed. That succession hail been established on observations 

 so abundant and so precise that it could withstand attack from any 

 quarter, and it had taken as firm and lasting a place among the solid 

 achievements of science as could be claimed for any physical 

 speculations whatsoever. Whether the time required for the 

 transaction of this marvellous earth-history was some millions of 

 years more or some millions of years less did not seem to the 

 geologists to be a question on which their science stood in antagonism 

 with the principles of natural philosophy, but one which the 

 natural philosophers might be left to settle at their own good 

 pleasure. 



For myself, I may be permitted here to say that T have never 

 shared this feeling of indifference and unconcern. As far back as 

 the year 1868, only a month after Lord Kelvin's first presentation of 

 his threefold argument in favour of limiting the age of the earth, 

 I gave in my adhesion to the propriety of restricting the geological 

 demands for time. I then showed that even the phenomena of 

 denudation, which, from the time of Hutton downwards, had been 

 most constantly and confidently appealed to in support of the incon- 

 ceivably vast antiquity of our globe, might be accounted for, at the 

 present rate of action, within such a period as 100 millions of years. ^ 

 To my mind it has always seemed that whatever tends to give more 

 precision to the chronology of the geologist, and helps him to a 

 clearer conception of the antiquity with which he has to deal, ought 

 to be welcomed by him as a valuable assistance in his inquiries. 

 And I feel sure that this view of the matter has now become general 

 among those engaged in geological research. Frank recognition is 

 made of the influence which Lord Kelvin's persistent attacks have 

 had upon our science. Geologists have been led by his criticisms to 

 revise their chronology. They gratefully acknowledge that to him 

 they owe the introduction of important new lines of investigation, 

 which link the solution of the problems of geology with those of 

 pliysics. They realize how much he has done to dissipate the former 

 vague conceptions as to the duration of geological history, and even 

 when they emphatically dissent from the greatly restricted bounds 

 within which he would now limit that history, and when they 

 declare their inability to perceive that any reform of their specula- 

 tions in this subject is needful, or that their science has placed 

 herself in opposition to the principles of physics, they none the less 

 pay their sincere homage to one who has thrown over geology, as 

 over so many other departments of natural knowledge, the clear light 

 of a penetrating and original genius. 



1 Trans. Geol. Soc. Glasgow, vol. iii, p. 189 (March 26, 1868). SirW. Thomson 

 acknowledged my adhesion in his reply to Huxley's criticism. Op. cit., p. 221. 



