Geological Society. 303 



any trains of a priori reasoning, based upon hypothetical analogies. 

 We must banish all a priori reasoning from the threshold of our 

 argument ; and the language of theory can never fall from our 

 lips with any grace or fitness, unless it appear as the simple enun- 

 ciation of those general facts, with which, by observation alone, we 

 have at length become acquainted. 



I should not have detained you one moment in enunciating pro- 

 positions such as these, had 1 not believed that their true import had 

 been partially misunderstood, and their spirit sometimes violated 

 in a recent work on the " Principles of Geology." Before I pro- 

 ceed with this remark, let me, however, first discharge a debt of 

 gratitude to the author, which, as yet, remains unpaid. Were I to 

 tell him of the instruction I received from every chapter of his 

 work, and of the delight with which I rose from the perusal 

 of the whole, I might seem to flatter rather than to speak the lan- 

 guage of sober criticism j but I should only give utterance to my 

 honest sentiments. His work has already taken, and will long 

 maintain a distinguished place in the philosophic literature of this 

 country ; higher praise than this I know not how to offer ; and 

 when, by publishing another volume (for which we all look with 

 earnest anticipation), he shall have recorded his discoveries in a 

 field of observation, almost his own he will then have reaped the 

 honour of being the first writer in our country to make known 

 a general system of " geological dynamics," a new province 

 gained by the advance of modern science. 



But Mr. Lyell appears not only as the historian of the natural 

 world, but as the champion of a great leading doctrine of the Hut- 

 tonian hypothesis : and it is to the effects produced on the princi- 

 ples of his work by the latter character, that I now wish to call 

 your attention, with all the freedom belonging to fair discussion 

 and the love of truth. It would, indeed, be a strange anomaly in 

 the history of physics, if the Huttonian hypothesis, framed by its 

 distinguished author, without any knowledge of the most important 

 facts of secondary geology, should require no new adjustments, 

 no limitation of its principles during the progress of discovery. 

 I cannot but regret, that from the very title page of his work, 

 Mr. Lyell seems to stand forward as the defender of a theory. An 

 hypothesis is indeed (when we are all agreed in receiving it) an 

 admirable means of marshalling scattered facts together, and ex- 

 hibiting them in all the strength of combination. But by those who 

 differ from us, an hypothesis will ever be regarded with just sus- 

 picion ; for it too often becomes, even in spite of our best efforts, 

 like a false horizon in astronomy, and vitiates all the great results of 

 our observations, however varied, or many times repeated. 



It cannot, I think, be doubted, that in the general statement 

 of his results, Mr. Lyell has, unconsciously, been sometimes warped 

 by his hypothesis, and that, in the language of an advocate, he 

 sometimes forgets the character of an historian. In reading his 

 graphic and eloquent descriptions of the mighty works of degrada- 

 tion yearly going on through the eastern shores of England, or of 

 the enormous weight of solid matter hourly rolled down by the 



Ganges 



