NA TURE 



361 



THURSDAY, FEBRUARY 17, 18S7 



THE ORIGIN OF MOUNTAIN RANGES 

 The Origin of Mountain Ranges considered Experi- 

 mentally, Structurally, Dynamically, and in Relation 

 to their Geological History. By T. M. Reade, C.E., 

 F.G.S. (London: Taylor and Francis, 1 886.) 

 'PHAT the skin of our mother Earth's face is wrinkled 

 and shrivelled, is one of the common facts of 

 fjeology. True it is that with fine feminine instinct she 

 strives to hide the ravages of time beneath a fair covering 

 of grass, moss, and herbage, and gracefully does her best 

 to make her old age comely ; and we love her for her skill in 

 covering up the signs of her years. But we are fain, directly 

 we look below the surface, to admit that the wrinkles are 

 there. And the parallel is not a fanciful one, for it has 

 long been a favourite theory among geologists that the 

 wrinkled skin of old age, and the foldings and bendings 

 which are everywhere to be discerned in the layers of the 

 skin of the earth, are due to similar causes. In both cases, 

 something underneath the skin, which in youth kept it 

 stretched and tense, has shrunk away, and the skin has 

 shrivelled up. In the case of the earth it is the gradual 

 contraction of the interior as it cools, which has caused it 

 to draw away from the outer shell ; and the crust, as it 

 follows down the shrinking nucleus, has to pack itself 

 into a smaller space, and consequently becomes crumpled 

 up. This e.vplanation is known as the " Contraction 

 Hypothesis." Numbering as it does many supporters, it 

 has had at the same time some vigorous opponents. In 

 his " Physics of the Earth's Crust," the Rev. Osmond 

 Fisher was led to the conclusion that the contraction 

 hypothesis would not furnish anything like the amount 

 of elevation that has actually occurred in the case of the 

 earth. We admire the ingenuity and elegance of Mr. 

 Fisher's mathematical work, but we cannot help re- 

 collecting Prof Huxley's warning, that mathematics is 

 like a mill, and that what you get out of it depends 

 entirely on what you put in. Mr. Fisher puts in a suppo- 

 sition made by Sir W. Thomson, as to the way in 

 which the earth cooled. There have been people bold 

 enough to think that in making this supposition a great 

 master of physics for once lent his name to an hypothesis 

 which is in itself physically not very probable ; and these 

 same people are inclined to hold that probably Mr. 

 Fisher's calculations tend to show that this is the case, 

 rather than that the contraction hypothesis is inadequate. 

 Capt. Dutton, of the United .States Geological Survey, 

 is another doughty opponent of the contraction hypo- 

 thesis. His notion as to what that hypothesis is appears 

 in the following passage, which is quoted in the volume 

 before us (p. 126, note) : — 



" The line of argument which is relied upon to 

 sustain a cooling globe proves, when pushed to its 

 consequences, that the great interior of the earth has 

 not as yet undergone any sensible amount of cooling. 

 The only cooling which that argument admits of has been 

 located in a thin external shell. ... In short, the cooling 

 would be only skin deep, while the nucleus is about as 

 hot as ever." 



This may be called " pushing an argument to its con- 

 sequences"; but if it be, that phrase certainly means, in 

 Vol. XXXV. — No. 903 



plain English, putting, of course unintentionally, into 

 your opponents' mouths, statements which they never 

 made. If it is asserted that the crust cools faster than 

 the nucleus, which is all the supporters of the contraction 

 hypothesis ask for, is this the same as saying that the 

 nucleus does not cool at all ? 



Now Mr. Mellard Reade joins the attack, and in an 

 elaborately illustrated volume of some 300 pages gives us 

 his reasons for dissenting from the contraction hypothesis, 

 and for preferring a modified form of the explanation put 

 forward originally by .Scrope and Babbage. These geo- 

 logists pointed out that whenever a great thickness of 

 sedimentary deposits was laid down the subterranean 

 surfaces of equal temperature would necessarily rise, the 

 increase in temperature would cause expansion, and as a 

 result of this 'a rise in the surface would follow. Mr. 

 Reade maintains that vertical elevation would not be the 

 only result, but that pressures would be set up in the 

 mass competent to produce folding, contortion, inversion, 

 crushing, and all the violent disturbances which are 

 found in mountain-chains and other disturbed portions of 

 the earth's crust. 



The book has two merits : it takes nothing for granted, 

 and it does not err on the side of assuming too much 

 knowledge on the part of its readers. But it is a question 

 whether virtue may not run to excess, and there is reason 

 to fear that this has been the case here, for a very large 

 part of the volume is taken up with the establish- 

 ment and illustration of physical facts of the most ele- 

 mentary character, and of geological truths which are to 

 be found in every text-book. For instance, Chapters III. 

 and IV. are devoted to the establishment of the facts that 

 metals and stone expand when their temperature is raised ; 

 that, when they are prevented by constraint from re- 

 lieving themselves by lateral expansion, they buckle up ; 

 and that if their elasticity, or, as the author prefers to call 

 it, their tensile strength, is small, they do not return to 

 their original shape on cooling. The cases quoted, and 

 the experiments which are illustrated by six full-page 

 plates, are apt and to the purpose ; they would be admir- 

 ably suited for illustrating class-teaching in an elementary 

 school. But it is hard to believe that any one could have 

 seriously thought they would be required by the class of 

 readers to whom the book is presumably addressed. 



Chapter V. opens with the statement that '' It has 

 been a subject of remark and wonder to more than one 

 eminent geologist that all the greatest mountain ranges 

 are, geologically speaking, so comparatively modern.'' 

 A broad generalisation like this deserves to have stress 

 laid upon it, but it has been so long one of the common 

 truths of geology, that it has ceased to be, if it ever was, 

 a source of wonder to any one who has an elementary 

 knowledge of the science. Indeed, there is an air of 

 naive surprise running through the book which now and 

 again moves a kindly smile as we read, and we feel it 

 refreshing to discover that truths, which have grown 

 somewhat hackneyed to the majority of geologists, still 

 retain a certain charm of novelty for the author. Thus 

 Mr. Reade seems in more than one passage to take a 

 little credit to himself for having discovered that what 

 are generally called " anticlinals " are really elongated 

 ellipsoidal domes — a fact which is rapidly brought home 

 to any one who happens to work for a few weeks in a 



