October 5, 1893] 



NATURE 



551 



be done with more expedition and greater cheapness. The 

 author in his paper certainly advocated abandoning both ham- 

 mering and cogging. In his paper he said, '■' Cogging, as it is 

 at present carried on, with its consequent reheating, is a 

 cumbersome, almost an ugly operation, and from the argu- 

 ments I have endeavoured to adduce, an unnecessary one. How 

 much smarter and cheaper it will be to taUe the ingots and roll 

 them right off into plates, and I commend this to your earnest 

 attention." Yet in the discussion which followed, Mr. Muir- 

 head said that he did not in his system do without cogging. 

 The point is one of considerable importance, and, Mr. Muir- 

 head's position as the manager of an important steel-producing 

 plant commands for him attention. If the same results can be 

 got from the ingot without cogging and reheating, undoubtedly 

 a great step in advance will have been taken ; but the majority 

 of steel-makers — perhaps we might say all, with the exception 

 of Mr. Muirhead — think that cogging or hammering is a 

 necessary though expensive process. Of course, if the author 

 can show that heis right, and the rest of the steel world wrong, 

 he will have performed a signal service to the industry. If we 

 were the owners of steel works, however, we should prefer the 

 experiments to be carried out by other manufacturers. It may 

 be added that what is known as the direct process of rolling is 

 not a new thing, and for Mr. Muirhead to succeed he will have 

 to introduce some entirely fresh element into his procedure. 



The last paper read at the meeting was Mr. Clarkson's con- 

 tribution, in which he described his ore sampling machine. It 

 would seem a small matter, at first glance, to sample ore, but 

 it is by no means an easy thing to do. The variations in 

 quality or composition are arbitrarily distributed, and it may 

 easily be that a sample made up from portions from several 

 different positions in the mass to be sampled, may not be a fair 

 representation of the whole. Machines have been before used, 

 by means of which small portions of a filling mass of ore may 

 be abstracted at regular intervals. It would be difficult to 

 describe this device without the aid of diagrams, but it may 

 be stated that though they appear to work fairly and 

 equitably at first sight, they are in reality partial in their selec- 

 tion. Mr. Clarkson has brought a trained mind to bear upon this 

 subject, and has produced a really scientific instrument. The 

 mass of ore is caused to fall in an annular stream, descending 

 into a hopper, which is made to revolve at great speed. By a 

 suitable mechanism small portions of the ore are abstracted at 

 regular intervals, and from the fact that the falling mass takes 

 Ihe form of anannulus in place of a solid stream, the tendency 

 of certain qualities to gather in the middle of the stream is 

 obviated. A small-sized apparatus was shown in the theatre, 

 and the author was able to practically demonstrate the accuracy 

 with which it worked, so far as the exact percentage of the 

 material abstracted from the whole was concerned. The 

 demonstration, it may be said, was perfectly successful. The 

 apparatus has another useful field in distribution of a mass into 

 equal parts, so that by it a number of bottles or boxes can be 

 filled without the tedious process of weighing being gone 

 through, and yet each receptacle will have its due share of the 

 material. The error of the ore separator is less than at 

 present. 



This was the last paper read at the meeting, which concluded 

 with the usual votes of thanks. 



THEORIES OF THE ORIGIN OF MOUNTAIN 



RANGES. 



tN his presidential address, delivered before the American 

 ■I- Association for the Advancement of Science this year. Prof. 

 Le Conte dealt with theories of mountain genesis — a subject 

 which lies at the very foundation of theoretical geology. Want 

 of space forbids us printing the address in full, hut the most 

 salient points are contained in the extracts from it that are here 

 given. 



Prof. Le Conte began by stating those fundamental features 

 of the structure of mountain ranges on which every true theory 

 of their origin must be founded. These features are : (l) Thick- 

 ness of mountain sediments ; (2) coarseness of mountain sedi- 

 ments ; (3) folded structure of mountains ; (4) cleavage struc- 

 ture ; (5) granite or metamorphic axis ; (6) asymmetric form. 

 Another type of mountain, the main characteristics of which 



NO. 1240, VOL. 48] 



are not included under the above heads, are those only found 

 in the Basin and Plateau regions, and therefore termed the 

 Basin legion type. In fact, "mountains may be divided into two 

 type?, vi?. mountains formed by folding of strata, and mountains 

 formed by tilting of crust-blocks. The "-tructure of the one is' 

 anticlinal or rf/clinal, of the oiher, monooXwivi. The Sierra pro- 

 bably belongs to both types. It was formed at the end of the 

 Jurassic as a mountain of the first type, but the whole Sierra 

 block was tilted up on its eastern side without folding at the 

 end of the Tertiary, and it then became also a mountain of the 

 second type. A complete theory must explain this type also : 

 but since from the exceptional character it must be regarded as 

 of subordinate importance, we shall be compelled to confine our 

 discussion to mountains of the usual type." 



Before going any further, however. Prof. Le Conte made a 

 digression in order to clearly lay down what he meant by 

 theory. After facts have been collected they must be explained, 

 and the explanation, which merely gives the laws of the imme- 

 diate phenomena in hand, is called the Formal Theory. The 

 next step towards the perfection of knowledge consists in ex- 

 plaining the cause of the^e laws, and is termed the Casual or 

 Physical Theory. The following is an illustration of this 

 distinction : — 



" All the phenomena of the drift are well explained by the 

 former existence of an ice-sheet moving southward by laws of 

 glacial motion, scoring, polishing, and depositing in its course. 

 This is the formal theory. But still the question remains. 

 What was the cause of the ice-sheet ? Was it due to northern 

 elevation, or to Aphelian winter concurring with great eccen- 

 tricity of the earth's orbit ? And if due to northern elevation, 

 what was the cause of that elevation ? A perfect theory must 

 answer all these questions." 



" .... I wish to keep clear in the mind these two stages of 

 theorising in the case of mountain origin. The formal theory 

 is already well advanced toward a satisfactory condition ; the 

 physical theory is still in a very chaotic state. But these two 

 kinds of theories have been often confounded with one another 

 in the popular and even in the scientific mind, and the chaotic 

 state of the latter has been carried over and credited to the 

 former also ; so that many seem to think that the whole subject 

 of mountain origin is yet wholly in the air, and without any 

 solid foundation." 



Bearing in mind that "a true formal theory, keeping close 

 to the immediate facts in hand, must pass gradually from 

 necessary inferences from smaller groups to a wider theory 

 which shall explain them all," Prof. Le Conte showed the 

 inferences that could be made from the characteristic features 

 of mountain stiucture, and he then grouped those inferences, 

 and summed up his views as to the mode of mountain formation 

 as follows : — 



Summary Statement of the Formal Theory. 



(l) " Mountain ranges, while in preparation for future birth, 

 were marginal sea-bottoms receiving abundant sediment from 

 an adjacent land-mass and slowly subsiding under the increasing 

 weight. (2) They were at first formed and continued for a time 

 to grow, by lateral pressure crushing and folding the strata 

 together horizontally and swelling them up vertically along a 

 certain line of easiest yielding. (3) That this line of easiest 

 yielding is determined by the hydrothermal softening of the 

 earth's crust along the line of thickest sedimentation. (4) That 

 this line by softening becomes also the line of greatest meta- 

 morphism, and by yielding the line of greatest folding and 

 greatest elevation. But (5) when the softening is very great, 

 sometimes the harder lateral strata are jammed in under the 

 crest, giving rise to fan-structure, in which case the most com- 

 plex foldings may be near but not at the crest. Finally (6) the 

 mountains thus formed will be asymmetric because the sedi- 

 mentary cylinder-lenses from which they originated were 

 asymmetric." 



Several American examples illustrating these views were 

 then given, and it was shown that eruptive phenomena, faults, 

 mineral veins, earthquakes, and other minor phenomena associ- 

 ated with mountains are well explained by them. To quote 

 Prof. Le Conte : "Leaving out the monoclinal type, which 

 seems to, belong to a different category, all the phenomena, major 

 and minor, of structure and of occurrences, connected with 

 mountains, are well explained by the theory of lateral pressure 

 acting on lines of thick sediments accumulated on marginal 



