THE AGE OF THE EARTH. 1 



By the Right Hon. Lord Rayleigh, F. R. S., and Others. 



The subject which we have met to consider to-day is encumbered 

 with past controversy. It can not be denied, I am afraid, that ex- 

 ponents of particular views in the past have laid too much emphasis 

 on their own particular way of looking at the problem without mak- 

 ing enough allowance for human fallibility. I shall try, so far as 

 possible, to avoid this pitfall. There has been a tendency on all 

 sides for specialists in one branch of science to consider themselves 

 free to disregard evidence drawn from a class of considerations 

 with which they are not familiar. I am sure that this is not the road 

 to truth. In attempting a problem of this kind, when we seek to 

 plumb into the depths of time, far beyond human experience, we 

 can not afford to neglect evidence drawn from any quarter, even if 

 it is not the kind of evidence which we find it most congenial to con- 

 template. A parallel case is that of a jury of plain men in a mur- 

 der trial. They may know nothing of medical jurisprudence, post- 

 mortem examinations, and so on. They may even consider the sub- 

 ject repellent ; but that does not exempt them from the duty of fully 

 considering and weighing such evidence to the best of their ability. 

 The witnesses in the trial have, however, to limit themselves to mat- 

 ters with which they are personally conversant. I will try to give 

 my evidence within these limits. 



The phrase "age of the earth," though rather vague, is perhaps 

 definite enough for our purpose. What we want to know is, how 

 long has the earth's surface been fitted for the habitation of living 

 beings; or, alternatively, how long has it taken to accumulate the 

 known series of geological formations? These questions are not 

 the same, but I do not think that we shall need to insist on the dis- 

 tinction this morning. 



Lord Kelvin's arguments depended on attempts to limit the length 

 of time during which the earth's surface temperature could have re- 



» Contributions to a joint discussion of the Sections of Mathematical and Physical 

 Science Geology, Zoology, and Botany of the British Association at Edinburgh on Sept. 

 16, 1921. Reprinted by permission from Nature, Oct. 27, 1921. 



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