192 APPENDIX. 



Kg. 18 represents a combination of fissures more or less like what must result from 



Fig. 18. 



An area of special elevation with its longitudinal and transverse fissures, Recording to Mr. Hopkins' hypothesis. 



conditions such as I have described: the curved boundary shows a partial area of greater 

 elevation, the broad lines which are not continuous represent fissures, longitudinal and transverse. 



In the memoir from which this abstract is made Mr. Hopkins describes the area of the 

 Wealden formation in the south-east of England, in which the features of disturbance cor- 

 respond in a most remarkable manner with the lines in this figure, — hence the legitimate 

 conclusion that their mode of formation corresponded with the assumed conditions, and that 

 these conditions are natural. As an actual cause Mr. Hopkins adopts the supposition of 

 extensive cavities within the solid crust of the earth, in which the expansion of fluid or gaseous 

 matters produces elevations. The phenomenon of faults necessitates (he conceives) the 

 existence of plastic matter below. For the production of such a result as that described in 

 the district of the Weald, Mr. Hopkins considers that one dominant effort of elevation must 

 have occurred by which all the lines were simultaneously struck out ; for the presence of 

 one fracture woidd interfere with the subsequent production of others. Should subsequent 

 research in any important degree alter the observations made by Mr. Hopkins in the district 

 of the Weald, his paper will retain its value as a discussion of one set of conditions. 



Besides the beautiful system of structure exhibited in this example of the Wealden area, 

 the most important inference to be drawn from it is the unity and completeness of the whole 

 phenomenon ; each feature lends itself to that next it ; there i nothing to suggest that this 

 elevation is but a partial product of a world-embracing tension. In connection with this 

 view the form of this area is most important, proving as it does the very considerable devia- 

 tion from rectilinear parallelism that can obtain among the main fissures of the same area 

 of elevation. This is so marked in the case of the Wealden elevation that M. dc Beaumont, 

 in support of his theory, had to deny the principal result of Mr. Hopkins' investigation — the 

 unity of the phenomenon — and to place the different parts of this area in different systems of 

 elevation, formed at different times. 



From the point of view taken bj Mr. Hopkins, the first object in examining an}' district is 

 to define the area affected by the same limited system of disturbance, and then the general 

 lines of dislocation, — the fissures which are the primary results of elevation. As for the 



