74 Lord Kelvin on the Age of the 



ago among British Geologists and Biologists; and which, I 

 must say, some of our chiefs of the present day have not yet 

 abandoned. Witness the Presidents of the Geological and 

 Zoological Sections of the British Association at its meetings 

 of 1893 (Nottingham), and of 1896 (Liverpool). 



Mr. Teall : Presidential Address to the Geological Section, 1 893. 

 " The good old British ship ' Uniformity,' built by Hutton and refitted 

 by Lyell, has won so mauy glorious victories in the past, and appears still 

 to be in such excellent righting trim, that I see no reason why she should 

 haul down her colours either to ' Catastrophe' or ' Evolution.' Instead, 

 therefore, of acceding to the request to ' hurry up ' we make a demand 

 for more time." 



Professor Poulton : Presidential Address to the Zoological Section, 1896. 

 " Our argument does not deal with the time required for the origin of 

 life, or for the development of the lowest beings with which we are 

 acquainted from the first formed beings, of which we know nothing. 

 Both these processes may have required an immensity of time ; but as we 

 know nothing whatever about them and have as yet no prospect of 

 acquiring any information, we are compelled to confine ourselves to as 

 much of the process of evolution as we can infer from the structure of 

 living and fossil forms — that is, as regards animals, to the development 

 of the simplest into the most complex Protozoa, the evolution of the 

 Metazoa from the Protozoa, aud the branching of the former into its 

 numerous Phyla, with all their Classes, Orders, Families, Genera, and 

 Species. But we shall find that this is quite enough to necessitate a very 

 large increase in the time estimated by the geologist." 



§ 15. In my own short paper from which I have read you 

 a sentence, the rate at which heat is at the present time lost 

 from the earth by conduction outwards through the upper 

 crust, as proved by observations of underground temperature 

 in different parts of the world, and by measurement of the 

 thermal conductivity of surface rocks and strata, sufficed to 

 utterly refute the Doctrine of Uniformity as taught by Hutton, 

 Lyell, and their followers ; which was the sole object of that 

 paper. 



§ 16. In an earlier communication to the Royal Society 

 of Edinburgh *, I had considered the cooling of the earth 

 due to this loss of heat ; and by tracing backwards the 

 process of cooling had formed a definite estimate of the 

 greatest and least number of million years which can 

 possibly have passed since the surface of the earth was 

 everywhere red hot. I expressed my conclusion in the 

 following statement f : — 



* " On the Secular Cooling of the Earth," Trans. Roy. Soc. Edinburgh, 

 vol. xxiii. April 28th, 1862, reprinted in Thomson and Tait, vol. iii. 

 pp. 468-485, and Math, and Phys. Papers, art. xciv. pp, 295-311. 



t " On the Secular Cooling of the Earth," Math, and Phys. Papers, 

 vol. iii. § 11 of art. xciv. 



