204 APPENDIX. 



But a simple fissure gives us a minimum of information. Mr. Hopkins tells us that his 

 whole system of fissures would result equally well from a deficiency as from an excess of 

 sustaining force, from depression as well as from elevation. M. de Beaumont also says for 

 his fissures that their immediate cause may be of several kinds, although the general cause 

 from which they are derived is uniform. Thus it would be altogether begging the question 

 to interpret fissures as evidence of elevation. What then are the geological (structural) evi- 

 dences of special elevation ? The difficulty seems to increase when we come to consider 

 the phenomena of disturbance and contortion. It seems of prima facie evidence that a 

 simple elevatory force, a force acting more or less vertically upw.ard, can only produce ten- 

 sion of strata at or near the surface ; unless indeed it be an expansive force within the crust 

 itself, in which case it will of course exercise a direct compressing action upon strata at a 

 distance, yet such a force would all the more readily find relief in vertical elevation. It 

 may then perhaps be assumed that the tangential forces, by which contortion of strata is 

 effected, must in almost every case be components of gravitation diverted through the arch 

 of the earth's crust. We still have the simpler cases of disturbance to consider. Here the 

 a priori answer seems inevitable, that a simple elevatory force would produce some form of 

 regular anticlinal — a tilting of the strata along a line of maximum effort. Mr. Hopkins 

 recognizes this necessity, and both in his theoretical diagram and in his section of the 

 Wealden area he represents an effect of this kind. This question has received much atten- 

 tion under the partial form of craters of elevation. It was then mainly discussed on the 

 ground of evidence, and the general verdict of opinion was against the existence of such 

 phenomena. The same decision may, I think, be arrived at against the greater case of axes 

 of elevation — lines of upheaval from which the strata are tilted on either side. The Hima- 

 laya, as far as we have seen of them, give no support whatever to this mode of upheaval. 

 It is much to be regretted that so eminent an authority as Mr. Hopkins, in putting forward 

 this theory of action as one exemplified in nature, did not suggest some explanation of the 

 o-eneral absence of this simple, and initially necessary effect, the only one from which we 

 could draw an inference in favour of this mode of upheaval. The instance of the Weald is 

 an insufficient basis for so important a conclusion. 



Thus it would seem that it is rather taken for granted, than proved, that true mountains, 

 elevated areas of special disturbance, are also areas of special elevation. The coincidence 

 is not so striking when we reflect that there are extensive areas of great elevation which are. 

 in no deo-ree areas of disturbance, and also, there are extensive areas of great and special 

 disturbance which are (at least at present) but little elevated. Of the former I have already 

 -given the Western Ghats as an example ; of the latter thei-e is a good instance in the grani- 

 toid schistose, and slaty rocks of South Behar, which only here and there form hills of incon- 

 siderable elevation. We cannot however get over the fact that regions of greatest elevation 

 are true mountains, and we must believe that the study of their structure will reveal the 

 secret of their formation. Mr. Rogers' classification of flexures forms an important contri- 

 bution to this study. The instances I have described of normal and of folded flexures in the 

 Sivalik strata must, I think, set at rest Mr. Rogers' difficulty as to the formation of such 

 flexures without great crust undulations. It is to be hoped that mathematical physicists 

 will not treat this all important subject with the disregard of which we have had to 

 complain in the theories of M. de Beaumont and Mr. Hopkins, but will come to the 



