12 KEPORT— 1892. 



established. It was impossible to conceive that the economy of the 

 planet could be maintained on any other basis. Without the circulatioa 

 of water the life of plants and animals would be impossible, and with 

 that circulation the decay of the surface of the land and the renovation 

 of its disintegrated materials are necessarily involved. 



As it is now so must it have been in past time. Hutton and Playfair 

 pointed to the stratified rocks of the earth's crust as demonstrations that 

 the same processes which are at work to-day have been in operation from' 

 a remote antiquity. By thus placing their theory on a basis of actual 

 observation, and providing in the study of existing operations a guide to 

 the interpretation of those in past times, they rescued the investigation of 

 the history of the earth from the speculations of theologians and cosmo- 

 logists, and established a place for it among the recognised inductive 

 sciences. To the guiding influence of their philosophical system the pro- 

 digious strides made by modern geology are in large measure to be 

 attributed. And here in their own city, after the lapse of a hundred 

 years, let us offer to their memory the grateful homage of all who have 

 profited by their labours. 



But while we recognise with admiration the far-reaching influence of 

 the doctrine of uniformity of causation in the investigation of the history 

 of the earth, we must upon reflection admit that the doctrine has been 

 pushed to an extreme perhaps not contemplated by its original founders. 

 To take the existing conditions of Nature as a platform of actual know- 

 ledge from which to start in an inquiry into former conditions was logical 

 and prudent. Obviously, however, human experience, in the few cen- 

 turies during which attention has been turned to such subjects, has been 

 too brief to warrant any dogmatic assumption that the various natural 

 processes must have been carried on in the past with the same energy 

 and at the same rate as they are carried on now. Variations in energy 

 might have been legitimately conceded as possible, though not to be 

 allowed without reasonable proof in their favour. It was right to refuse 

 to admit the operation of speculative causes of change when the pheno- 

 mena were capable of natural and adequate explanation by reference to 

 causes that can be watched and investigated. But it was an error to take 

 for granted that no other kind of process or influence, nor any variation 

 in the rate of activity save those of which man has had actual cognisance, 

 has played a part in the terrestrial economy. The uniformitarian writers 

 laid themselves open to the charge of maintaining a kind of perpetual 

 motion in the machinery of Nature. They could find in the records of the 

 earth's history no evidence of a beginning, no prospect of an end. They 



