Darwin, after describing the great earthquakes which he had experienced in South America, and the evidence of their connection with volcanic outbursts, proceeded to show that earthquakes originated in fractures, gradually formed in the earth's crust, and were accompanied by movements of the land on either side of the fracture. In conclusion he boldly advanced the view "that continental elevations, and the action of volcanoes, are phenomena now in progress, caused by some great but slow change in the interior of the earth; and, therefore, that it might be anticipated, that the formation of mountain chains is likewise in progress: and at a rate which may be judged of by either actions, but most clearly by the growth of volcanoes." ("Proc. Geol. Soc." Vol. II. pages 654-60.)Lyell's account ("Life, Letters and Journals of Sir Charles Lyell, Bart.", edited by his sister-in-law, Mrs Lyell, Vol. II. pages 40, 41 (Letter to Leonard Horner, 1838), 2 vols. London, 1881.) of the discussion was as follows: "In support of my heretical notions," Darwin "opened upon De la Beche, Phillips and others his whole battery of the earthquakes and volcanoes of the Andes, and argued that spaces at least a thousand miles long were simultaneously subject to earthquakes and volcanic eruptions, and that the elevation of the Pampas, Patagonia, etc., all depended on a common cause; also that the greater the contortions of strata in a mountain chain, the smaller must have been each separate and individual movement of that long series which was necessary to upheave the chain. Had they been more violent, he contended that the subterraneous fluid matter would have gushed out and overflowed, and the strata would have been blown up and annihilated. (It is interesting to compare this with what Darwin wrote to Henslow seven years earlier.) He therefore introduces a cooling of one small underground injection, and then the pumping in of other lava, or porphyry, or granite, into the previously consolidated and first-formed mass of igneous rock. (Ideas somewhat similar to this suggestion have recently been revived by Dr See ("Proc. Am. Phil. Soc." Vol. XLVII. 1908, page 262.).) When he had done his description of the reiterated strokes of his volcanic pump, De la Beche gave us a long oration about the impossibility of strata of the Alps, etc., remaining flexible for such a time as they must have done, if they were to be tilted, convoluted, or overturned by gradual small shoves. He never, however, explained his theory of original flexibility, and therefore I am as unable as ever to comprehend why flexiblility is a quality so limited in time.
"Phillips then got up and pronounced a panegyric upon the "Principles of Geology", and although he still differed, thought the actual cause doctrine had been so well put, that it had advanced the science and formed a date or era, and that for centuries the two opposite doctrines would divide geologists, some contending for greater pristine forces, others satisfied, like Lyell and Darwin, with the same intensity as nature now employs.
"Fitton quizzed Phillips a little for the warmth of his eulogy, saying that he (Fitton) and others, who had Mr Lyell always with them, were in the habit of admiring and quarrelling with him every day, as one might do with a sister or cousin, whom one would only kiss and embrace fervently after a long absence. This seemed to be Mr Phillips' case, coming up occasionally from the provinces. Fitton then finished this drollery by charging me with not having done justice to Hutton, who he said was for gradual elevation.
"I replied, that most of the critics had attacked me for overrating Hutton, and that Playfair understood him as I did.
"Whewell concluded by considering Hopkins' mathematical calculations, to which Darwin had often referred. He also said that we ought not to try and make out what Hutton would have taught and thought, if he had known the facts which we now know."It may be necessary to point out, in explanation of the above narrative, that while it was perfectly clear from Hutton's rather obscure and involved writings that he advocated slow and gradual change on the earth's surface, his frequent references to violent action and earthquakes led many--including Playfair, Lyell and Whewell--to believe that he held the changes going on in the earth's interior to be of a catastrophic nature. Fitton, however, maintained that Hutton was consistently uniformitarian. Before the idea of the actual "flowing" of solid bodies under intense pressure had been grasped by geologists, De la Beche, like Playfair before him, maintained that the bending and folding of rocks must have been effected before their complete consolidation.
