1 88 APPENDIX. 



a prominent object in simple orography (delineation of contour), yet are of but very subordi- 

 nate consequence in the discussion of mountain-structure. From one of the many partial 

 points of view in physical geography we find even elevation made little of. We find Dr. Hooker 

 in his 'Himalayan Journals', Vol. H., p. 387, speaking of the "true Himalayan axis" as a 

 question of watershed, making " mere elevation of secondary importance." The approxi- 

 mate determination of a line of elevated country is in itself of much interest in physical 

 geography, but has little or no independent meaning in plij'sical geology, and if so applied 

 such facts are almost sure to lead to error. It were easy to adduce instances of geological 

 speculations founded upon no other basis than these subordinate facts. The example of Von 

 Humboldt, at a time when geology was in its infancy, has given much encouragement to what 

 must now be considered an unscientific confusion of ideas. 



We must then at once draw a clear dictinction between these two essentially different 

 aspects of mountain phenomena. As simple conditions of the earth's surface, affecting the 

 actual life of the planet in the distribution of climates and of living creatures, the form and 

 the position of mountains are the only features that we need consider; and the appropriate 

 grouping of mountains for this purpose should rest largely on the single fact of continuity. 

 Such is the aspect that belongs to physical geography. 



Physical geology assumes a very different point of view. Its object is to investigate the mode 

 of origin of mountains. The facts which may throw light on this question are very numerous 

 and yet obscure, and an appropriate definition of a mountain system in this sense might be — all 

 elevations, whether continuous or not, which are the result of a single act of nature. For 

 example, from considerations of climatology and natural history, as facts of physical geography, 

 the Alps or the Pyrenees form a simple and independent group, having no natural affinity to 

 the Himalayas, or the mountains of Northern Africa ; but from the geological point of view, 

 affinities have been asserted between these chains, and may, for aught we can yet say, exist ; 

 and further, from the same point of view, several quite distinct systems of upheaval have been 

 supposed to be represented in the single orographical area of the Alps. 



It is to be regretted that our best writers on physical geography, still following in the track 

 made by the great founder of the science, Von Humboldt, confound distinct branches of scientific 

 investigation. The result is an incongruity in their productions, viz., a general predominance 

 of a purely geographical arrangement with frequent vague reference to geological systems. 

 What is simple is obscured by them, and a most objectionable looseness is introduced into an 

 investigation that demands the utmost clearness and patience. Even supposing our knowledge 

 of mountain-formation to be complete, the distinction I point out would still obtain. The 

 confusion is the more objectionable when we know it to be based upon a theory that is very 

 far from being established, and that is opposed bj' views leading to diametrically opposite results. 

 We will presently see that this contradictory relation exists between the views of disturbing 

 agencies adopted by such high authorities as De Beaumont on one side, and Babbage and 

 Herschell on the other : the theory of the former aims at universal symmetry, that of the 

 latter legalizes disorder. 



In approaching the question of mountain-structure, — how it is produced — the first ques- 

 tion that presents itself is to what extent the causes of geologi- 



General and local causes. ' 



cal disturbances are general or local. By general causes are 



meant, agencies that affect the whole earth, such as the slow refrigeration of the mass, or, 



tidal phenomena in a fluid internal mass; local causes are such as proceed from the local 



