ANNIVERSARY ADDRESS OF THE PRESIDENT. xlv 



immense when contrasted with a brief sera of 3000 or 5000 years. 

 The real point on which the whole controversy turns, is the rela- 

 tive amount of work done by mechanical force in given quantities of 

 time, past and present. Before we can determine the relative in- 

 tensity of the force employed, we must have some fixed standard by 

 which to measure the time expended in its development at two di- 

 stinct periods. Dr. Whewell has justly observed, that " mechanical 

 power retains its amount, however much it be distributed through 

 time and divested of the character of extraordinary violence *," — a 

 principle which should never be lost sight of when we contrast the 

 effects of the historical with those of antecedent epochs. It is not 

 the magnitude of the effects, however gigantic their proportions, 

 which can inform us in the slightest degree whether the operation 

 was sudden or gradual, insensible or paroxysmal. It must be shown 

 that a slow process could never in any series of ages give rise to the 

 same results. 



The advocate of paroxysmal energy might assume an uniform and 

 fixed rate of variation in times past and present for the animate 

 world that is to say, for the dying-out and coming-in of species, 

 and then endeavour to prove that the changes of the inanimate world 

 have not gone on in a corresponding ratio. But the adoption of such 

 a standard of comparison would lead, I suspect, to a theory by no 

 means favourable to the pristine intensity of natural causes. That 

 the present state of the organic world is not stationary can, I think, 

 be fairly inferred from the fact, that some species are known to have 

 become extinct in the course even of the last three centuries, and 

 that the exterminating causes always in activity, both on the land 

 and in the waters, are very numerous ; also, because man himself is 

 an extremely modern creation ; and we may therefore reasonably sup- 

 pose that some of the mammalia now contemporary with man, as 

 well as a variety of species of inferior classes, may have been recently 

 introduced into the earth, to supply the places of plants and animals 

 which have from time to time disappeared. But granting that some 

 such secular variation in the zoological and botanical worlds is going 

 on, and is by no means wholly inappreciable to the naturalist, still it 

 is certainly far less manifest than the revolution always in progress 

 in the inorganic world. Every year some volcanic eruptions take 



* Quart. Journ. Geol. Soc. vol. iii. p. 231. 



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