Dec. II, 1873J 



NATURE 



that his Grace formerly thought it necessary to assure us 

 that Time could do nothing by itself, " nothing except by 

 the aid of its great ally Force — Force working in Time." 

 Well, «/e shall not quarrel about the use of words, but 

 cheerfully admit that the change which has become per- 

 ceptible in the opinions of the Duke of Argyll is wholly 

 the result of " Force working in Time," and not a very 

 long time, for it cannot be stretched out beyond five years. 

 Surely if the lapse of so brief a space, with all the amount 

 of Force which we can crowd into it, can have modified 

 geological opinions which certainly seemed as solidly and 

 unalterably fixed as his own Ben More itself, it can hardly 

 be too much to hold that by the end of another histnmi 

 still further modification may justify the confident belief 

 that his Grace may still come to join the "younger 

 school " heart and hand. We can assure him a jubilant 

 welcome. 



But it may be asked what is the nature of this present 

 alteration of view? In brief, it may be put thus : the 

 Duke of Argyll finds that, after all, denudation is one of 

 those disagreeable facts which will insist on being promi- 

 nent — " chiels that winna ding." He has discovered that 

 it really has had some share in the shaping of the present 

 outlines of the land. He now admits in words " that the 

 forms of hill and valley which preceded the commg-on 

 of glacial conditions [during the Ice age] had been them- 

 selves determined in a large degree by previous denuda- 

 tions." And even though this general admission is 

 neutralised by statements which follow it, it is most 

 welcome as an indication doubtless of the effect of those 

 " more extended opportunities of observation " which his 

 Grace tells us he has since enjoyed, and on the continu- 

 ance of which our hopes of his secession to the ranks of 

 the " younger school " are mainly based. 



The Duke of Argyll appeals once more to the details 

 of geological structure. Jlost gladly do we accede to the 

 appeal. He points to the contorted condition of the older 

 rocks as evidence of the extent to which they have been 

 affected by subterranean movements. But no geologists 

 are more familiar with these facts than his maligned 

 " younger school." He conceives that it was after such 

 movements that the forces of denudation began to work. 

 Most assuredly ; this has been explained over and over 

 again. He affirms that '• so long as such hills and moun- 

 tains last at all, and wherever they are exposed to view, 

 they bear upon them the unmistakeable impress of their 

 origin and of the mighty subterranean forces to which 

 their structure is due." This sentence is rather ambiguous. 

 If it means that contorted rocks retain evidence of contor- 

 tion, such an obvious truism was hardly worth a sentence 

 to itself. If it means that a mountain made of contorted 

 rocks has had its form determined at the time of contor- 

 tion, the statement is mere assertion and a begging of the 

 very question to be proved. 



In the same address the noble president declares that 

 " denudation has done its work along the lines deter- 

 mined by upheaval, by fracturCj and by unequal subsid- 

 ence." This has never been denied by anyone. A main 

 object of my book was to show how, by means of denu- 

 dation along such lines, much of the present contour of 

 Scotland has been produced. Again we are told — " All 

 sedimentary beds must have h.ad an edge somewhere ; 

 and if they are lifted into a vertical position and the 

 edges come to be exposed, the removal of a small amount 

 of material may result in a horizontal surface, or in sur- 

 faces cutting across the lines of structure at every variety 

 of angle." If the Duke intends this explanation to apply 

 not to a mere hand specimen, but to any district of con- 

 voluted and vertical rocks, such as the hills of Wales or 

 the Southern Uplands or Highlands of Scotland, he 

 cannot have noticed the string of physical absurdities 

 which it involves. The rocks are often vertical, or nearly 

 so, for miles at a stretch. Could we put them into some- 

 thing like their original horizontal or gently inclined posi. 



tion their present edges would end off in a cliff many 

 miles high. Can his Grace expect anyone to believe that 

 the beds, which certainly " must have had an edge some- 

 where," ever ended off in that fashion ? But this would 

 be only a part of the feat. In actual fact the rocks have 

 been violently contorted, so that a series several hundreds 

 or even thousands of feet in thickness is folded again and 

 again upon itself The present surface has been cut across 

 these foldings, and in great part has its inequalities inde- 

 pendent of them. If we could flatten these curved rocks 

 out again from their present condition they would show 

 a series of deep sharp troughs separated by steep pyra- 

 midal ridges of flat strata. And from the Duke of 

 Argyll's teaching we should learn that this wonderful 

 arrangement was the normal plan in old times of laying 

 down sediment which, instead of always going to the 

 bottom and filling up the hollows as it does nowadays, 

 contrived then to ascend, layer after layer, like the tiers 

 of the Great Pyramid, as if it were under the impulse not 

 of mere gravity or of the play of ocean currents, but of the 

 methodical action of organisms like the coral polyps. 

 We shoukl further learn that these neatly-shaped sand 

 and mud ridges and troughs were so accurately laid down 

 that when subterranean forces came into action and 

 crumpled the whole up, every ridge popped conveniently 

 into a trough below, as if a trap-door had been opened for 

 its reception, and with such nice adjustment as to bring 

 its top to the same general level as the bottom of the 

 former troughs I 



The truth is, and, in common fairness I am bound 

 frankly to state it, that such assertions as these with 

 which I am dealing, could never be made if geological 

 structure were really understood and kept in view. This 

 is a matter of science, and is only to be mastered by the 

 same patient toil which is required in other scientific 

 inquiries. Moreover, it is by no m;ans so easily mastered 

 as it seems to be. The first absolute requisite for over- 

 coming our ignorance, is to reduce our facts to the test of 

 ocular proof and measurement. Let us construct a sec- 

 tion .across the tract of which we would master the struc- 

 ture, and to avoid risks of error from exaggeration of 

 proportion, let us begin by making the section as nearly 

 as possible on a true scale, that is, giving the same value 

 to length as to height. With the outline of the ground 

 accurately traced we may then, section in hand, insert 

 upon it at the proper places, and with the true angle of 

 dip, such rocks as we be able to see exposed. Having 

 fixed these data in this patient way, we may expect with 

 some confidence to understand and fill in the geological 

 structure of the ground for ourselves, and to make it in- 

 telligible and credible to others. Until we have gone 

 through such a training ourselves, or have learnt ade- 

 quately to appreciate what it is from the labours of others, 

 we have no right to utter an opinion on the relations 

 between geological structure and external form, for we 

 are destitute of one of the necessary qualifications for 

 dealing with the problem. 

 ' The greater part of the recent address of the president 

 I of the Geological Society deals with the traces of ice- 

 action in this country, and the manner in which they are 

 to be accounted for. In his remarks upon this subject, 

 the Duke again places himself in opposition to the views 

 of the "jounger school," and expresses opinions from 

 which every member of that school would, I aai sure, em- 

 phatically dissent. It is no part of my present purpose 

 to enter upon these. I cannot, however, pass by one 

 statement in the address. His Grace asserts that these 

 restless "younger geologists" have recently made a most 

 complete change of front. He therefore directs his attack 

 against this new position. He says that they no longer 

 maintain the existing systems of hill and valley to have 

 been cut out of the solid by an enormous glacier, but 

 admit the general contour of the country to have been 

 very much the same before the Ice age as after it, all the 



