NA TURE 



{Dec. 



1873 



EARTH-SCULPTURE * 

 III. 



I DO not consider it necessary to defend my facts. They 

 are familiar enough to the geologists of this country, as 

 displayed more or less plainly in every district of our 

 island. I am at present concerned with the counter- 

 statements which the Duke of Argyll would put in their 

 place. 



He states his belief that the Highland mountains have 

 had their contour mainly given to them by " upheavals, 

 subsidences, and lateral pressures, which have folded 

 them and broken them into their present shapes." A be- 

 lief of any kind must be founded on evidence of some 

 sort, and that evidence must be produced if the owner of 

 the belief desires that it should be accepted by others 

 besides himself. What evidence, then, does his Grace 

 furnish as the basis on which he expects that his 

 "belief" is to supersede what he is pleased -to term 

 "the extravagant theories of the younger glacialists".? 

 Having shown " the antecedent improbabilities in- 

 volved in the extreme theories of erosion," he states 

 that he " proceeds to test them on the field of fact." 

 We follow him anxiously to the field in question, and find 

 that his so-called facts are stated in such words as these ; 

 " Loch Fyne . . . occupies, as I believe, the bed (si'c) of 

 an immense fault." " The transverse valley of Loch Eck 

 lies across a steep anticlinal, and is due, in my opinion, 

 to the extreme tension to which the crystalline rocks have 

 been subjected." "The Pass of Awe is a rupture and 

 chasm." These, and other similar assertions regardiniT 

 various parts of the Highlands are confidently expressed, 

 but they are accompanied by no evidence by which their 

 accuracy may be tested. In truth, the "facts" which 

 his Grace adduces in support of his "belief" are only 

 other " beliefs " and " opinions " of his own. They 

 may be correct or the reverse, but they cannot legiti- 

 mately be adduced as evidence in a scientific argument. 

 But they are very far from correct. I utterly deny, for 

 example, the assertion that Loch Fyne lies along the bed 

 of an immense fault, and I ask the Duke of Argyll to 

 try to prove that it does so. Nay more, I challenge him 

 to produce a geological section which would bear a mo- 

 ment's examination on the ground, in which he can show 

 the coincidence of a valley with a line of fault in any part 

 of his own county of Argyll. That cases of this coin- 

 cidence may be found I do not doubt, but the search for 

 them will be useful in teaching his Grace how excep- 

 tional they are. 



The Duke of Argyll does indeed offer some explanatory 

 statements regarding some of his assertions of fact. For 

 instance, with regard to Loch Awe, he dwells on the in- 

 chnations of the slates and the intrusion of the porphyries 

 among them as evidence that the present contour has 

 been directly the result of subterranean convulsion, and 

 he triumphantly adduces these and similar appearances 

 "ignored" by myself as a demonstration of the truth of 

 his " belief." But any one who knows the H ighland rocks 

 at all may well smile when he is told that a geologist who 

 had ever been over the ground, even in the most cursory 

 way, requires to have these phenomena pointed out to him. 

 In reality I had already granted the existence of these, 

 and far more wonderful evidences of underground move- 

 ments, for I knew the Highland rocks well, and had 

 mapped their structure over leagues of ground from 

 the mountains of Sutherland to the moors of Foifar, and 

 the headlands of Islay. I was therefore perfectlv famiHar 

 wiih the phenomena to which the Duke of Argyll so con- 

 fidently refers. But I had learned more about them than 

 merely their tale of subterranean turmoil. I had found 

 that they did not bear directly on the origin of hill and 

 valley at all. I had traced everywhere evidence that what 



'Opening Address to the Edinburgh CJeological Society, by Prof. Gcikic, 

 F.R.b. (comiitued from p. 91). 



we now see of intruded granite or curved slate has been 

 laid bare only after the removal of hundreds and thou- 

 sands of feet of rock under which they once lay. His 

 Grace, it would seem, has still this lesson to learn, and until 

 he has mastered it, and, apart from any theory but simply 

 as a matter of demonstrable fact, has realised what it 

 involves and how vain is the attempt to connect the con- 

 torting and hardening of the rocks with the present sur- 

 face features of the country, argument with him on this 

 question seems hardly possible. 



Again, I had quoted the m.ountain Ben Lawers, with its 

 flanking hollow in Loch Tay, as a typical example of the 

 kind of evidence which could be abundantly adduced 

 from all parts of the Highlands to. show the relation be- 

 tween geological structure and external form, and to 1 

 prove from under what an enormous mass of removed 

 rock the present surface of the Highlands has appeared. 

 I gave a section to show at a glance the broad facts of 

 the case — a section from which no conclusion is pos- 

 sible but that which I drew. But here, once more, 

 the Duke of Argyll's belief in the all-powerftd effi- 

 cacy of granite and igneous rocks, or his thraldom 

 to what he calls " the influence of a preconceived 

 theory," brings out in well-marked prominence that 

 obliquity of vision which prevents him from seeing 

 anything but convulsion and fracture. He scents intru- 

 sive rocks of some sort along the south bank of Loch 

 Tay. It would be vain to remonstrate that this alleged 

 influence of the igneous rocks is, to say the least, as pure 

 "invention and imagination" as anything which the 

 " younger school " could readily supply, or that the denu- 

 dation of that region is a momentous fact to be looked in 

 the face and explained, not to be dismissed or denied, no 

 matter what our " theory " or " belief " may be regarding 

 the origin of granite. Without further ceremony, the 

 proofs of cnonnous denudation at Ben Lawers and Loch 

 Tay, together with their luckless advocate, are all bundled 

 off with the summary judgment, so happily appropriate 

 to its own author, " I attach no value whatever to a theory 

 which passes over and ignores this class of facts alto- 

 gether." 



The dogmatic assertions which the Duke of Argyll 

 makes regarding the influence of granite and other rocks 

 upon the surface, and as to the existence of fractures and 

 depressions along the line of valley and glen, are really 

 most flagrant examples oi At pe/itio principii. In effect, 

 his Grace tells us, " The ' inventions and imaginations ' ■ 

 of these younger men are based upon 'assumed facts' 

 which ' are, in my opinion, to a large extent purely hypo- 

 thetical.' I am ' suspicious of the influence which a pre- 

 conceived theory has had on their estimate of evidence.' 

 I therefore 'attach no value whatever' to their state- 

 ments, and do net consider it necessary to lose time in 

 weighing what they actually mean by this denudation of 

 theirs, and all which, as they contend, must flow from it. 

 My belief is that valleys are due to fractures and depres- 

 sions. The Highlands abound in valleys, and therefore 

 it must be evident to everyone capable of forming an 

 opinion on the subject, that they abound also in proofs of 

 fracture and depression." 



In the foregoing remarks I have been dealing only with 

 the Duke of Argyll's paper of February 1S68, which in 

 his recent vigorously-worded address he cites as still un- 

 answered, and which, therefore, we may suppose still to 

 expresshis views. And yet no one can peruse that ad- 

 dress without perceiving that it betokens a considerable 

 change of opinion. Especially gratifying must it be to 

 that "younger school" of geologists against which the 

 Duke has so vehemently lifted up his protest, to observe 

 that the lapse of time which he would not allow to have 

 had much denuding effect upon the rocks, has yet been 

 able to strip ofi" from himselt some of that crust of pre- 

 conceived "theory" against which no argument or ad- 

 verse fact could once make any impression. It is true 



