APPENDIX. 



193 



eecondary results, such as faults, anticlinals, lines of curvature, &c, Mr. Hopkins only states 

 that, as immediate consequences of the Assuring of the crust, they follow laws of distribution 

 corresponding to the fissures. Fig. 19 represents a transverse section of an area of elevation at 

 the instant of rupture, Fig. 20 an imaginary subsequent condition.* However secondary they 



Fig. 19. 





~1 



UuLaJ 



Diagram cross-section of an area of special elevation, at the moment of fracture. — (Hopkins.) 



Fig. 20. 



Section showing subsequent condition of same area.— (Hopkins.) ■. 

 may be, these features are all important in practice, and it is to be regretted that Mr, Hopkins 

 does not say more about them. But the term fissure is vague, and, as a fact, a simple fissure 

 is rare to meet with, and difficult to detect. Indeed, in the area of elevation described by 

 Mr. Hopkins, the features identified by him as corresponding to the theoretical lines of longi- 

 tudinal fissure are, almost without exception, lines of fault or of contortion, i. e., something 

 more than mere fissures. In the case of the transverse fissures, this term is more strictly 

 applicable. Some explanation of the phenomena of flexure is especially called for in an 

 identification of natural conditions, for those features are rarely if ever absent, and it 

 often seems impossible to account for them upon the sole condition of elevation, and 

 without some influence of lateral force more than is prima, facie derivable from the 

 supposition of a simple elevatory force. The inspection of the actual sections of the 

 Wealden district given by Mr. Hopkins will indicate what I mean. I take one as an example 

 (Fig. 21). When from the consideration of such a simple case as the elevation of the Weald, 



Fig. 21. 



A cross-section of the Wealden area. — (Hopkins.) 



* These figures are taken from a paper by Mr. Darwin, as quoted from Mr. Hopkins* paper in the Cambridge 

 Phil, Trans., to which work I could not procure access. 



A 1 



