8 Lord Kelvin on the Age of the 



probable that the sun has not illuminated the earth for 100,000,000 years, 

 and almost certain that he has not done so for 500,000,000 years. As for 

 the future, we may say with equal certainty, that the inhabitants of the 

 earth cannot continue to enjoy the light and heat essential to their life 

 for many million years longer, unless new sources, now unknown to us, 

 are prepared in the great storehouse of creation." 



I said that in the sixties and I repeat it now ; but with 

 charming logic it is held to be inconsistent with a later state- 

 ment that the sun has not been shining 60,000,000 years ; 

 and that both that and this are stultified by a still closer 

 estimate which says that probably the sun has not been 

 shining for 30,000,000 years ! And so my efforts to find some 

 limit or estimate for Geological Time have been referred to 

 and put before the public, even in London daily and weekly 

 papers, to show how exceedingly wild are the wanderings 

 of physicists, and how mutually contradictory are their con- 

 clusions, as to the length of time which has actually passed 

 since the early geological epochs to the present date. 



Dr. Haughton further goes on — 



" This result (100 to 500 million years) of Professor Thomson's, although 

 very liberal in the allowance of time, has offended geologists, because, having 

 been accustomed to deal with time as an infinite quantity at their disptosal, 

 they feel naturally embarrassment and alarm at any attempt of the science 

 of Physics to place a limit upon their speculations. It is quite possible 

 that even a hundred million of years may be greatly in excess of the 

 actual time during which the sun's heat has remained constant." 



§ 5. Dr. Haughton admitted so much with a candid open 

 mind; but he went on to express his own belief (in 1865) thus: — 



" Although I have spoken somewhat disrespectfully of the geological 

 calculus in my lecture, yet I believe that the time during which organic 

 life has existed on the earth is practically infinite, because it can be shown 

 to be so great as to be inconceivable by beings of our limited intelligence." 



Where is inconceivableness in 10,000,000,000 ? There is 

 nothing inconceivable in the number of persons in this room, 

 or in London. We get up to millions quickly. Is there any- 

 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. 



§ 6. The following statement is from Professor Jukes's 

 ' Students' Manual of Geology : ' — 



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

 results must of course be taken to be inconceivably 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." 



