NA TURE 



60 1 



THURSDAY, APRIL 25, 1S95. 



CONTROVERSIAL GEOLOGY, 

 'ollecled Papers on some Controverted Questions of 



Geology. By Joseph Prestwich, D.C.L. (Oxon), F.R.S., 



F.G.S., Corr. Inst. France (Acad. Sci.) ; Acad. 



R. Lyncei, Rome; Imp. Geol. Inst., Vienna ; Acad. 



Roy., Brussels ; Amer. Phil. Soc, Philad. ; &c. 



(London : Macmillan and Co., 1895.) 



"XiriTH respect to the main facts of Geology, we 



V V geologists are in general of one opinion, but 

 with respect to the explanation of many of those facts, 

 ve hold very divergent opinions." In these opening words 

 jf his preface, the author explains and justifies the publi- 

 ation of this collection of essays. Prof Prestwich's 

 position, as the acknowledged doyen among British 

 geologists, demands that these articles— the latest fruits 

 of his ripe experience — should receive the most thought- 

 ful consideration from his fellow geologists ; but, quite 

 apart from the position and authority of their author, 

 all of the mem:)irs included in this volume are of the 

 greatest value as contributions to science ; and in reading 

 them it is difficult to say whether we are more impressed 

 by the wealth of knowledge or the literary grace which 

 they display. 



The key-no:e of the volume is struck in the first 

 article, "The Position of Geology — a Chapter on Uni- 

 formitarianism," published in the Nineteenth Century 

 of October 1S93 In this short and admirably written 

 essay, the author clearly defines his own attitude with 

 respect to the doctrme of uniformity. He credits most 

 English geologists with a belief in an absolute uniformity 

 60th in kind and degree, vihWe he and many continental 

 geologists, who fully accept uniformity in kind, altogether 

 reject the notion that the actions going on at the present 

 day can be accepted as measures of the rate of similar 

 changes in the past. We cannot help thinking, however, 

 in reading this essay, that the issue is not quite so simple 

 as the author implies. The strictest uniformitarian would 

 never maintain that no action that has taken place in past 

 geological times could possibly have exceeded in violence, 

 or in the effects produced by it, the phenomena which 

 we may have happened to have witnessed during that 

 century or two, in which systematic studies of terrestrial 

 changes have been carried on. In 1783 a volcano in 

 Iceland threw out lava having a volume equal to that of 

 Mont Blanc ; and in 1 8S3, another volcano in the Sunda 

 Straits projected materials to the height of sixteen miles 

 into the atmosphere. Now no geologist would maintain 

 that there could not possibly have occurred, in the long 

 periods of the past, more violent eruptions than these. 

 The uniformitarian only asks that in the explanation of 

 the past we confine ourselves to operations of the same 

 order of mignitude, as those novv occurring upon the 

 earth. We shouUl be surely justified, for example, in 

 asking for very definite evidence that in past times a 

 single geological eruption had thrown out materials equal 

 to the volume of the whole .'Mpine chain, or that another 

 had projected materials to the height of 150 miles. If a 

 gorge can be shown to have been cut by an existing river 

 in 1000 years, it would hardly be legitimate to infer that a 

 NO. 1330, VOL. 51] 



similar gorge was cut in ten years by a river of 100 times 

 the volume, unless at the same time it were shown that 

 there were very strong reasons for believing that rivers of 

 the proportions assumed actually existed in the past. 



Prof Prestwich puts what he conceives to be the 

 position of the unifurmitarians in the following simile : — 

 " What if it were suggested that the brick-built pyramid 

 of Hawara had been laid brick by brick by a single 

 workman .' Given time, this would not be beyond the 

 bounds of possibility. But nature, like the Pharaohs, had 

 greater forces at her command to do the work better and 

 more expeditiously than is admitted by the uniformi- 

 tarians." We cannot accept the parallel as a just one. 

 Large brick structures are not at the present day erected 

 by a single bricklayer, and the historian — who is equally 

 uniformitarian in his practice with the geologist — does 

 not feel called upon to suggest any such improbable 

 origin for a pyramid. But if, on the contrary, it were 

 asserted that the pyramids are so vast that they must 

 have been erected by a race of beings of larger stature 

 and greater physical strength than the men of the pre- 

 sent day, a position would be taken up similar to that of 

 the opponents of a rational uniformitarianism. The 

 historian justly asks that before such a view be accepted, 

 it shall be shown that the work of pyramid-building 

 could not be performed by ordinary men working in 

 sufficient numbers for a long period of time. Nor would 

 the historian be very greatly concerned if it were argued 

 that by ordinary men such a task of pyramid building 

 might extend over several reigns, or would even require 

 centuries for its accomplishment. Every historian, in 

 fact, takes up the same attitude as the uniformitarian 

 geologist when he refuses to credit the men of bygone 

 ages with gigantic stature, prodigious strength, abnormal 

 wisdom, or extraordinary longevity. 



While, however, we demur to the principles and ideas 

 ascribed by the author of this volume to the uniformi- 

 tarians, we gladly accept his work as an additional proof, 

 if such were required, that old-fashioned " catas- 

 trophism " in geology is now quite extinct. More than 

 this, we think that the protests and cautions of so 

 distinguished and able a reasoner as Prof. Prestwich will 

 render a real service to geology in calling attention to 

 somewhat unwarrantable assumptions that have been 

 made by some theorists. With our author's complaint 

 against what he justly compares io the closure, 3.i applied 

 by physicists and mathematicians to the legitimate specu- 

 lations of the geologist, we entirely sympathise. " It 

 would," as he justly says, " be an unfortunate day for any 

 science to have free discussion and inquiry barred by 

 assumed postulates, and not by the ordinary rules of 

 evidence as established by the facts, however divergent 

 the conclusions to which those facts lead may be from 

 the prevailing belief" 



The second essay in the volume is a weighty criticism 

 of the astronomical theory of glacial epochs. The onlv 

 objection which we think c.in be taken to the essay is 

 that the author identifies the upholders of this theory 

 with the uniformitarians. The late Sir Charles Lyel 

 never accepted the theory of Mr. CroU, and many holding 

 the strongest uniformitarian views have always main- 

 tained that geological facts are opposed to any of those 



