i8 4 HUTTONIAN THEORY 



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 commencement, but he estimated that the 

 surface of the globe could not have consolidated less 

 than twenty millions of years ago, for the rate of in- 

 crease 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 has unconcernedly believed to be 

 ample has somehow taken to itself wings and disap- 

 peared. When the geologist was suddenly awakened 

 by the energetic warning of the physicist, who assured 

 him that he had enormously overdrawn his account 

 with past time, it was but natural under the circum- 

 stances that he should think the accountant to be 

 mistaken, who thus returned to him dishonoured the 

 large drafts he had made on eternity. He saw how 

 wide were the limits of time deducible from physical 

 considerations, how vague the data from which they 

 had been calculated. And though he could not help 

 admitting that a limit must be fixed beyond which 

 his chronology could not be extended, he consoled 



