18 REPORT— 1892. 



define it. The progress of research continually furnished additional evi- 

 dence of the enormous duration of the ages that preceded the coming 

 of man, while, as knowledge increased, periods that were thought to have 

 followed each other consecutively were found to have been separated by 

 prolonged intervals of time. Thus the idea arose and gained universal 

 acceptance that, just as no boundary could be set to the astronomer in 

 his free range through space, so the whole of bygone eternity lay open to 

 the requirements of the geologist. Playfair, re-echoing and expanding 

 Hutton's language, had declared that neither among the records of the 

 earth nor in the planetaiy motions can any trace be discovered of the 

 beginning or of the end of the present order of things ; that no symptom 

 of infancy or of old age has been allowed to appear on the face of Nature, 

 nor any sign by which either the past or the future duration of the uni- 

 verse can be estimated ; and that although the Creator may put an end, as 

 He no doubt gave a beginning, to the present system, such a catastrophe 

 will not be brought about by any of the laws now existing, and is not 

 indicated by anything which we perceive. This doctrine was naturally 

 espoused with warmth by the extreme uniformitarian school, which re- 

 quired an unlimited duration of time for the accomplishment of such slow 

 and quiet cycles of change as they conceived to be alone recognisable in 

 the records of the earth's past history. 



It was Lord Kelvin who, in the writings to which I have already re- 

 ferred, first called attention to the fundamentally erroneous nature of 

 these conceptions. He pointed out that from the high internal tem- 

 perature of our globe, increasing inwards as it does, and from the rate of 

 loss of its heat, a limit may be fixed to the planet's antiquity. He showed 

 that so far from there being no sign of a beginning, and no prospect of 

 an end to the present economy, every lineament of the solar system bears 

 witness to a gradual dissipation of energy from some definite starting- 

 point. No very precise data were then, or indeed are now, available for 

 computing the interval which has elapsed since that remote commence- 

 ment, but he estimated that the surface of the globe could not have con- 

 solidated less than twenty millions of years ago, for the rate of increase 

 of temperature inwards would in that case have been higher than it 

 actually is ; nor more than 400 millions of years ago, for then there would 

 have been no sensible increase at all. He was inclined, when first dealing 

 with the subject, to believe that from a review of all the evidence then 

 available, some such period as 100 millions of years would embrace the 

 whole geological history of the globe. 



It is not a pleasant experience to discover that a fortune which one 



