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globe, be bound to each other by laws like those which govern 

 the movements of the heavenly bodies — then every material combi- 

 nation we now see must re-appear with all its complicated relations 

 after the lapse of some long period of time. But would not such a 

 supposition be now regarded as the mere wantonness of hypothetical 

 extravagance ? And let it not be said, that it is only in the greater 

 combinations on the surface of tlie earth that we are to look for re- 

 turning cycles. Great and small have no meaning, except in reference 

 to us and our conceptions. The earth is an atom in comparison with 

 the visible creation; and all we now behold may be but as an atom in 

 comparison of that which is unseen ; and the meanest combinations 

 of material things submitted to our senses propagate their influence 

 through all space co-extensive with gravitation, and play their part 

 in keeping up the stability of the universe. 



To the supreme Intelligence, indeed, all the complex and mutable 

 combinations we behold, may be but the necessary results of some 

 simple law, regulating every material change, and involving within 

 itself the very complications, which we, in our ignorance, regard as 

 interruptions in the continuity of Nature's work. In contempla- 

 tions of this kind our understanding is lost among the stern doctrines 

 of philosophical necessity. But, as far as regards us and our facul- 

 ties, there is no such thing on earth as undeviating moral or phy- 

 sical necessity. For as, in morals, necessity is made, in part, at 

 least, subordinate to the freedom of human will ; so, in physics, the 

 continued action of immutable causes may and does co-exist with 

 mutable phenomena. 



The study of the great physical mutations on the surface of the 

 earth is the business of geology. But who can define the limits of 

 these mutations ? They have been drawn by the hand of Nature, 

 and may be studied in the record of her works — but they never 

 have been, and never will be fixed, by any guesses of our own, or by 

 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 I 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 



