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all other ardent generalizations of an advancing science, must ever 

 be regarded but as shifting hypotheses to be modified by every new 

 fact, till at length they become accordant with all the phenomena of 

 nature. 



Tn retreating where we have advanced too far, there is neither com- 

 promise of dignity nor loss of strength ; for in doing this, we partake 

 but of the common fortune of every one who enters on a field of in- 

 vestigation like our own. All the noble generalizations of Cuvier, 

 and all the beautiful discoveries of Buckland, as far as they are the 

 results of fair induction, will ever remain unshaken by the progress of 

 discovery. It is only to theoretical opinions that my remarks have 

 any application. 



Different formations of solid rock, however elevated and contorted, 

 can never become entirely mixed together ; and the very progress of 

 degradation commonly lays bare all the elements of their structure. 

 But diluvial gravel may be shot off from the flanks of a mountain chain, 

 during one period of elevation, and become so confounded with the 

 detritus of another period, that no power on earth can separate them : 

 and every subsequent movement, whether produced by land floods or 

 any other similar cause, must continually tend still further to mingle 

 and confound them. The study of diluvial gravel is, then, not only 

 one of great interest, but of peculiar difficulty and nice discrimina- 

 tion : and in the very same deposit, we may find the remains of 

 animals which have lived during different epochs in the history of the 

 earth. 



Bearing upon this difficult question, there is, I think, one great 

 negative conclusion now incontestably established — that the vast 

 masses of diluvial gravel, scattered almost over the surface of the 

 earth, do not belong to one violent and transitory period. It was in- 

 deed a most unwarranted conclusion, when we assumed the contem- 

 poraneity of all the superficial gravel on the earth. We saw the 

 clearest traces of diluvial action, and we had, in our sacred histories, 

 the record of a general deluge. On this double testimony it was, that 

 we gave a unity to a vast succession of phenomena, not one of 

 which we perfectly comprehended, and under the name diluvium, 

 classed them all together. 



To seek the light of physical truth by reasoning of this kind, is, in 

 the language of Bacon, to seek the living among the dead, and will 

 ever end in erroneous induction. Our errors were, however, natural, 

 and of the same kind which led many excellent observers of a former 

 century to refer all the secondary formations of geology to the Noachian 

 deluge. Having been myself a believer, and, to the best of my power, 

 a propagator of what I now regard as a philosophic heresy, and having 

 more than once been quoted for opinions I do not now maintain, I 

 think it right, as one of my last acts before I quit this Chair, thus 

 publicly to read my recantation. 



VVe ought, indeed, to have paused before we first adopted the dilu- 

 vian theory, and referred all our old superficial gravel to the action 

 of the Mosaic flood. For of man, and the works of his hands, we 

 have not yet found a single trace among the remnants of a former 

 world entombed in these ancient deposits. In classing together di- 



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