518 Progress of Geological Science. [Nov. 



terial change, and involving within itself the very complications, which we, in our 

 ignorance, regard as interruptions in the continuity of Nature's work. In contem- 

 plations of this kind, our understanding is lost among the stern doctrines of philoso- 

 phical necessity. But, as far as regards us and our faculties, there is no such thing 

 on earth as undeviating moral or physical 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 

 phaenomena. 



" The study of the great physical mutations on the surface of the earth is the busi- 

 ness 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 



Du t 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 d 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 enunciation of those general facts, with which, by observation alone, 

 we have at length become acquainted." 



The above observations are introductory to the Professor's objections to Mr. 

 Lyell's system of " geological dynamics," which, although highly praised, as a new 

 province of the science studied with immense research, and pregnant with facts ne- 

 cessary to be borne in mind, in the explanation of every observed phaenomenon, 

 .seems to him to have been strained beyond the limits of logical inference, in its 

 application to the vast efforts of displacement and deposition, of the gigantic 

 epoch of geology. 



" Mr. Lyell appears not only as the historian of the natural world, but as the 

 champion of a great leading doctrine of the Huttonian hypothesis ; in the lan- 

 guage 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* or the Missisippi, I have 

 fancied, that the earth was sliding from under my feet, and that it would soon pass 

 away, like the sand of an hour-glass, beneath the waters of the ocean. 



" But are there no antagonist powers in nature to oppose these mighty ravages — 

 no conservative principle to meet this vast destructive agency ? The forces of de- 

 gradation very often of themselves produce their own limitation. The mountain 

 torrent may tear up the solid rock, and bear its fragments to the plain below: but 

 there its power is at an end, and the rolled fragments are left behind to a new 

 action of material elements. And what is true of a single rock is true of a moun- 

 tain chain ; and vast regions on the surface of the earth, now only the monuments 

 of spoliation and waste, may hereafter rest secure under the defence of a thick 

 vegetable covering, and become a new scene of life and animation. 



" It well deserves remark, that the destructive powers of nature act only upon 

 lines, while some of the grand principles of conservation act upon the whole sur- 

 face of the land. By the processes of vegetable life, an incalculable mass of solid 

 matter is absorbed, year after year, from the elastic and non-elastic fluids circulat- 

 ing round the earth, and is then thrown down upon its surface. In this single 

 operation, there is a vast counterpoise to all the agents of destruction. And the 

 deltas of the Ganges and the Missisippi are not solely formed at the expense of the 



* For a correction of the estimate of Major Rennell, see the pages of this Journal and 

 of the Gleanings. 



