CilXXXVIii] concluding eemaeks. 631 



metals, it will follow that tliose formed farthest from the surface will 

 usually require the longest time before they can be exposed superficially^ 

 In order to bring them into view, or within reach of the miner, a greater 

 amount of upheaval and denudation must take place in proportion as 

 they have lain deeper when first mowed. A considerable series of geo- 

 logical revolutions must intervene before any part of the fissure, which 

 has been for ages in the proximity of the plutonic rocks, so as to receive 

 the gases discharged from it when it was cooling, can emerge into the 

 atmosphere. But I need not enlarge on this subject, as the reader will 

 remember what was said in the 30th, 34th, and 37th chapters, on the 

 chronology of the volcanic and hypogene formations. 



Concluding Remarks. — The theory of the origin of the hypogene 

 rocks, at a variety of successive periods, as expounded in two of the 

 chapters just cited, and still more the doctrine that such rocks may be 

 now in the daily course of formation, has made and still makes its way. 

 but slowly, into favor. The disinclination to embrace it has arisen 

 partly from an inherent obscurity in the very nature of the evidence of 

 plutonic action when developed on a great scale, at particular periods 

 It has also sprung, in some degree, from extrinsic considerations; many 

 geologists having been unwilling to believe the doctrine of the transmu- 

 tation of fossiliferous into crystalline rocks, because they were desirous 

 of finding proofs of a beginning, and of tracing back the history of our 

 terraqueous system to times anterior to the creation of organic beings. 

 But if these expectations have been disappointed, if we have found it 

 impossible to assign a limit to that time throughout which it has pleased 

 an Omnipotent and Eternal Being to manifest his creative power, we 

 have at least succeeded beyond all hope in carrying back our researches 

 to times antecedent to the existence of man. We can prove that man 

 had a beginning, and that, all the species now contemporary with man, 

 and many others which preceded, had also a beginning, and that, conse- 

 quently, the present state of the organic world has not gone on from all 

 eternity, as some philosophers have maintained. 



It can be shown that the earth's surface has been remodelled again 

 and again ; mountain chains have been raised or sunk ; valleyS formed, 

 filled up, and then re-excavated; sea and land have changed places; 

 yet throughout all these revolutions, and the consequent alterations of 

 local and general climate, animal and vegetable life has been sustained. 

 This has been accomplished without violation of the laws now governing 

 the organic creation, by which limits are assigned to the variability of 

 species. The succession of living beings appears to have been continued 

 not by the transmutation of species, but by the introduction into the 

 earth from time to time of new plants and animals, and each assemblage 

 of new species must have been admirably fitted for the new states of 

 the globe as they arose, or they would not have increased and multiplied 

 and endured for indefinite periods.'^ 



