Ixxiv PROCEEDINGS OF THE GEOLOGICAL SOCIETY. 



reply, that no internal cause conld account for any such infinite re- 

 currence, more than for unlimited permanence of temperature. Such 

 infinite recurrence could only be attributed to the external causes — 

 solar and stellar radiation. If to the former, the quantity of heat ra- 

 diating from the sun must be subject to enormous periodical changes, 

 but still without permanent diminution ; if to the latter, it might be 

 attributed either to similar periodical changes in the radiation of the 

 stars, or more probably to a change in the position of the solar system 

 with reference to them, as I have explained in my paper on Terrestrial 

 Temperature. But we shall probably all agree in regarding such 

 hypotheses as extremely unsatisfactory, and utterly unfit to be made 

 the foundation on which a great speculative theory may rest. But 

 however unsatisfactory they may be, I repeat that we have no other 

 alternative but that of adopting one of them, consistent with the 

 most fundamental properties of heat, if we maintain the theory of 

 non-progression in the strict sense in which I have used the term. 

 And, having placed the theory in this point of view, I might leave 

 it there, without venturing into those speculations which assume the 

 properties of the matter, constituting the stellar universe, to be the 

 same as those which characterize the matter of our planet. Views 

 founded on such assumptions ought to be advanced with diffidence, 

 and held with cautious reserve ; but if, with such reservation, we as- 

 sume the sun and the stars to have the same properties as our own 

 planet, with respect to the generation and emission of heat, we must 

 conclude that those bodies must be subject to permanent changes of 

 temperature, as well as the earth itself, from the effect of radiation. 

 In such case even solar and stellar radiation must necessarily fail to 

 preserve the earth from that permanent change of temperature which 

 would constitute essentially a state of progression. In fact, adopting 

 the assumption just stated respecting the nature of the sun and stars, 

 and reasoning from all we know of the properties of matter and of 

 heat, I am unable in any manner to recognize the seal and impress of 

 eternity stamped on the physical universe, regarded as subjected to 

 those laws alone by which we conceive it at present to be governed. 



The rejection of the doctrine of progression, both with respect to 

 animate beings and inanimate matter, would seem to lead almost 

 necessarily to the opinion, that the sequence of periodical changes, 

 similar to those which have happened within the period of which we 

 can trace the geological history, has been of infinite duration. It 

 would appear to involve the rejection of the notion of a beginning of 

 the actual physical condition of our planet. If not, the earth must 

 have been created at once, at some finite distance of time, as fit a 

 dw^elling-place for organic beings, as it has been rendered, according 

 to the theory of progression, only by a long series of superficial ope- 

 rations. In other words, phsenomena must have existed as the 

 immediate act of creation, and anterior to the operation of physical 

 causes, which it is the very essence of geology to account for by re- 

 ference to those causes. This would be to sap the foundations on 

 which alone geology can rest as a physical science. 



I would again, Gentlemen, carefully remind you that I have been 



