14 THE EIGHT HON. LORD KELVIN, G.C.V.O., ON 



thing inconceivable in 30,000,000 as the population of 

 England, or in 38,000,000 as the population of Great Britain 

 and Ireland, or in 352,704,863 as the population of the British 

 Empire? Not at all. It is just as conceivable as half a 

 million years or 500 millions. 



§ (3. The following statement is from Professor Jukes's 

 Students Ilamial of Geology : — 



"The time required for such a slow process to effect such enormous 

 ]-esults must of course be taken to be inconceiAabl^y great. The word 

 'inconceivably' is not here used in a vague but in a literal sense, to 

 indicate that the lapse of time required for the denudation that has 

 produced the present surfaces of some of the older rocks, is vast beyond 

 any idea of time which the human mind is capable of conceiving." 



" Mr. Darwin, in his admirably reasoned book on the origin of species, 

 so full of information and suggestion on all geological subjects, estimates 

 the time required for the deniulation of the rocks of the Weald of Kent, 

 or the erosion of space between the ranges of chalk hills, known as the 

 North and South Downs, at three hundred millions of ytars. The 

 grounds for forming this estimate are of couise of the vaguest de- 

 scription. It may be possible, perhaps, that the estimate is a hundred 

 times too great, and that the real time elapsed did not exceed three 

 million years, but, on the other hand, it is just as likely that the time 

 which actually elapsed since the first commencement of the erosion till it 

 was neai'ly as complete as it now is, was really a hundi'ed times greater 

 than his estimate, or thirty thousand millions of years." 



§ 7. Thus Jukes allowed estimates of anything from 

 3 millions to 30,000 milhons as the time which actually 

 passed during the denudation of the Weald. On the other 

 hand Professor Phillips in his Rede lecture to the University 

 of Cambridge (1860), decidedly prefers one inch per annum 

 to Darwin's one inch per century as the rate of erosion ; and 

 says that most observers would consider even the one inch 

 per annum l^oo small for all but the most in^■incible coasts I 

 He thus, on purely geological grouncis, reduces Darwin's 

 estimate ot the time to less than one one-hundredth. And, 

 reckoning the actual thicknesses of all the known geological 

 strata of the earth, he finds 9() million years as a possible 

 estimate for the antiquity of the base of the sti-atified rocks ; 

 but be gives reasons for supposing that this maybe an over- 

 estimate, and he finds that from stratigraphical evidence 

 alone, we may regard the antiquity of life on the earth as 

 possibly between 38 millions and iM) millions of years. 

 Quite lately a very careful estimate of the antiquity of 

 strata containing remains of life on the earth, has been 

 given by Professor Sollas, of Oxford, calculated according 

 to stratigraphical principles which had been pointed out 



