ADDRESS. 15 



Though Hutton and Playfair believed in periodical catastrophes, and 

 indeed required these to recur in order to renew and preserve the 

 habitable condition of our planet, their successors gradually came to 

 view with repugnance any appeal to abnormal, and especially to violent 

 manifestations of terrestrial vigour, and even persuaded themselves that 

 such slow and comparatively feeble action as had been witnessed by man 

 could alone be recognised in the evidence from which geological histoiy 

 must be compiled. Well do I remember in my own boyhood what a 

 cardinal article of faith this prepossession had become. We were taught 

 by our great and honoured master, Lyell, to believe implicitly in gentle 

 and uniform operations, extended over indefinite periods of time, though 

 possibly some, with the zeal of partisans, carried this belief to an extreme 

 which Lyell himself did not approve. The most stupendous marks of 

 terrestrial disturbance, such as the structure of great mountain chains, 

 were deemed to be more satisfactorily accounted for by slow movements 

 prolonged through indefinite ages than by any sudden convulsion. 



What the more extreme members of the uniformitarian school failed 

 to perceive was the absence of all evidence that terrestrial catastrophes 

 even on a colossal scale might not be a part of the present economy of 

 this globe. Such occurrences might never seriously affect the whole 

 earth at one time, and might return at such wide intervals that no 

 example of them has yet been chronicled by man. But that they have 

 occurred again and again, and even within comparatively recent geologi- 

 cal times, hardly admits of serious doubt. How far at different epochs and 

 in various degrees they may have included the operation of cosmical influ- 

 ences lying wholly outside the planet, and how far they have resulted from 

 movements within the body of the planet itself, must remain for further 

 inquiry. Yet the admission that they have played a part in geological 

 history may be freely made without impairing the real value of the 

 Huttonian doctrine, that in the interpretation of this history our main 

 guide must be a knowledge of the existing processes of terrestrial change. 



As the most recent and best known of these great transformations, the 

 Ice Age stands out conspicuously before us. If any one sixty years ago 

 had ventured to affirm that at no very distant date the snows and 

 glaciers of the Arctic regions stretched southwards into France, he would 

 have been treated as a mere visionary theorist. Many of the facts to 

 which he would have appealed in support of his statement were already 

 well known, but they had received various other interpretations. By 

 some observers, notably by Hutton's friend, Sir James Hall, they were 

 believed to be due to violent debacles of water that swept over the face 



