486 



NATURE 



[September 21, 1893 



SECTION C. 



GEOLOGY. 



Opening Address by J. J. H. Teall, M.A., F.R.S., 

 Sec.G. S., President of the Section. 



It is a striking and remarkable fact that, although enormous 

 progress has been made in petrographical science during; the 

 last hundred years, there has been comparatively little advance 

 so far as broad, general theories relating to the origin of rocks 

 are concerned. In Hutton's "Theory of the Earth," the out- 

 lines of which were published in 1788, the following operations 

 are clearly recognised :^The degradation of the earth's surface 

 by aqueous and atmospheric agencies; the deposition of the 

 dibris beneath the waters of the ocean ; the consolidation and 

 metamorphosis of the sedimentary deposits by the internal heat 

 and by the injection of mohen mineral matter ; the disturbance 

 and upheaval of the oceanic deposits ; and, lastly, the forma- 

 tion of rocks by the consolidation of molten material both at the 

 surface and in the interior of the earth. 



Hutton regarded these operations as efficient causes ordained 

 for the purpose of producing an earth adapted to sustain animal 

 and vegetable life. His writings are saturated with the teleo- 

 logical philosophy of the age to which they belong, and some of 

 his arguments strike us, therefore, as strange and inconclusive ; 

 moreover, the imperfect state of the sciences of chemistry and 

 physics occasionally led him into serious error. Notwithstand- 

 ing these imperfections, we are compelled to admit, when 

 viewing his work in the light of modern knowledge, that we 

 can find the traces, and sometimes far more than the traces, of 

 those broad general theories relating to dynamical geology 

 which are current at the present day. 



If Hutton had contented himself with proving the reality of 

 the agencies to which reference has been made it is probable 

 that his views would have been generally accepted. But he 

 went much further than this, and boldly mainlained that one or 

 other of these agencies, or several combined, would account for 

 all the phenomena with which the geologist has to deal. It was 

 this that gave rise to the controversial fire which blazed up with 

 such fury during the early years of this century, and whose 

 dying embers have not yet been extinguirhed. 



The views of Hutton were in strong contrast to those of 

 Werner, the celebrated professor of mineralogy at Freiberg, to 

 whom science owes a debt of gratiiude as great as that due to 

 the Scottish physician. The value of a man's work must not 

 simply be judged by the truth of the theory which he holds. I 

 consider that the Wernerian theory — by which I understand a 

 reference to the early stages of planetary evolution for the pur- 

 pose of explaining certain geological facts — has been on the 

 wane from the time it was propounded down to the present day ; 

 but I claim to be second to none in my admiration for the know- 

 ledge, genius, and enthusiasm of the illustrous Saxon professor. 

 The uniformitarian doctrines of Hutton gave a very decided 

 character to the theoretical views of British geologists during the 

 middle of the century, in consequence of the eloquent support 

 of Lyell ; but of late there has been a tendency to hark back 

 to a modified form of Wernerism. This tendency can, I think, 

 be largely traced to the recognition of evolution as a factor in 

 biology and physical astronomy. The discoveries in these 

 sciences may necessitate a modification of the views held by 

 some of the extreme advocates of uniformitarianism. This 

 admission, however, by no means carries with it the conclusion 

 that the methods based on the doctrine of uniformitarianism 

 must be discarded. If I read the history of geology aright, 

 every important advance in the theoretical interpretation of 

 observed facts relating to physical geology has been made by 

 the application of these methods. It does not, of course, 

 follow that the progress in the future will be exactly along the 

 same lines as that in the past ; but, if I am right in the opinion 

 I have expressed, it is a strong reason for adhering to the old 

 methods until they have been proved to be inapplicable to at 

 least some of the facts with which the physical geologist has to 

 deal. Let us consider for a moment whether the recognition of 

 evolution as a factor in biology and physical astronomy gives 

 an h priori probability to some form of Wernerism. 



The period of time represented by our fossiliferous records is 

 perhaps equivalent to that occupied by the evolution of the verte- 

 brata, but all the great subdivisions of the invertebrata were 

 living in the Cambrian period, and must have been differentiated 

 in still earlier times. Is it not probable, therefore, that the 

 fossiliferous records at present known represent a period in- 



significant in comparison with that during which life has existed 

 upon the earth? Again, is it not probable that the period 

 during which life has existed is a still smaller fraction of that 

 which has elapsed since the formation of the primitive crust? 

 And if so, what a priori reason have we for believing that the 

 rocks accessible to observation contain the records of the early 

 stages of the planet's history ? But the advocates of the diluted 

 foru.s of Wernerism which find expression in geological writings 

 at the present day almost invariably refer to recent speculations 

 in cosmical physics. The views of astronomers have always had 

 a powerful influence on those of geologists. Hutton wrote at a 

 time when the astronomical world had been profoundly affecled 

 by Lagrange's discovery, in 1776, of the periodicity of the 

 secular changes in the forms of the planetary orbits. The 

 doubts as to the stability of the solar system which the recogni- 

 tion of these changes had inspired were thus removed, and 

 astronomers could then see in the physical system of the 

 universe " no vestige of a beginning, — no prospect of an end." 

 Now it is otherwise. Tidal friction and the dissipation of 

 energy by the earth and by the sun are each referred to as fixing 

 a limit to the existing conditions. I have not the knowledge 

 necessary to enable me to discuss these questions, and I will 

 therefore admit, for the sake of ari;ument, that the phenomena 

 referred to indicate the lines along which the physical evolution 

 of our planet has taken place ; but does it follow that geologists 

 should desert a working hypothesis which has led to brilliant 

 results in the past for one which has been tried again ami again 

 and always found wanting? 



If there were absolute unanimity amongst mathematical 

 physicists, it might be necessary for us to reconsider our posi- 

 tion. This, however, is not the case. After referring to the 

 argument from tidal friction, Prof. Darwin, in his address 

 to the Mathematical and Physical Section for i886. Fays : — "On 

 the whole, then, I can neither feel the cogency of the argument 

 from tidal friction itself, nor, accepting it, can I place any re- 

 liance on the limits which it assigns to geological history." In 

 reviewing the argument from the secular cooling of the earth, 

 he points out that the possibility of the generation of heat in the 

 interior by tidal friction has been ignored, and that the thermal 

 data on which the calculations are based are not sufficiently 

 complete to remove all reasonable doubt. He regards tlie case 

 depending on the secular cooling of the sun as the strongest ; 

 but it is evident that, in view of undreamt-of possibilities, he 

 would not allow it to have much weight in the face of adverse 

 geological evidence. In conclusion he says: — "Al. hough 

 speculations as to the future course of science are usually 

 of little avail, yet it seems as likely that meteorology 

 and geology will pass the word of command to ccsmical 

 physics as the converse. At present our knowledge of a 

 definite limit to geological time has so little precision that we 

 should do wrong to summarily reject any theories which appear 

 to demand longer periods of time than those which now 

 appear allowable. In each branch of science hypothesis forms 

 the nucleus for the aggregation of observation, and as long as 

 facts are assimilated and co ordinated we ought to follow our 

 theory." Now, my point is that the uniformitarian hypothesis, 

 as applied to the rocks we can examine, has assimilated and co- 

 ordinated so many facts in the past, and is assimilating and co- 

 ordinating so many new discoveries, that we should continue to 

 follow it, rather than plunge into the trackless waste of cos- 

 mogonical speculation in pursuit of what may after all prove to 

 be a will-o'-the-wisp. 



As an additional illustration of the want of agreement 

 amongst mathematical physicists on questions relating to the 

 earth, I may refer to certain papers by Mr. Chree. ' This 

 author maintains that the modern theory of elasticity points to 

 the conclusion that if a spherical globe, composed of a nearly 

 incompressible elastic solid of the size of the earth, were set 

 rotating as the earth is rotating, it would take the form which 

 the earth actually possesses. How is the question of the fixity 

 of the earth's axis afiecied by Mr. Chree's researches, and by 

 the recent observations which prove a simultaneous change of 

 latitude, in opposite directions, in Europe and at Honolulu? 

 If geological facts point to a shifting of the position of the axis, 

 is there any dynamical reason why they should not receive due 

 consideration ? Geologists want as much freedom as possible. 

 We do not object to any limitations which are necessary in the 

 interest of science, and we cordially welcome, and as a matter 



' C. Chree, " On Some Applications of Physics and Mathematics to 

 Geology," /*////. Mag., vol. xxxii. (1891), pp. 233, 342. 



NO. 1247, VOL. 48] 



