408 Captain F. W. Hutton on the Phenomena of the 



district (Trans. Geol. Soc. Ser. 2, vol. vii.), Mr. W. Hopkins 

 showed that if a district is elevated by the upward pressure of an 

 underlying fluid mass, tension will be produced in the rocks, 

 which will cause the formation of two systems of fissures — one 

 parallel to the major axis of the area undergoing elevation, the 

 other at right angles to its periphery ; and he takes the Wealden 

 district as an example agreeing in all respects with his deduc- 

 tions, thus proving that the Weald anticlinal has been formed 

 in this manner. Now, without for a mofoent questioning the 

 effects which Mr. Hopkins has shown must necessarily follow 

 from such an upward pressure, it is quite allowable to inquire 

 whether he has been happy in selecting the Wealden area as 

 an illustration, and whether the Herschel-Babbage theory will 

 not give a far better explanation of the phenomena. In his 

 able description of the district, Mr. Hopkins represents the 

 chalk escarpment which surrounds it, and w^hich is supposed 

 to be parallel with the periphery of the elevating fluid, as being 

 traversed by transverse faults or fissures which have originated 

 the valleys in which the rivers now flow that drain the area of 

 the Weald, these fissures being those of his second system. He 

 also describes longitudinal minor anticlinal axes, or "lines of 

 elevation,^' as he calls them, parallel to the major axis of the ele- 

 vated district; and these, curiously enough, he considers as an- 

 swering to his first system of fissures. Mr. Hopkins candidly 

 acknowledges that one only of the transverse fissures of his se- 

 cond system, that between Battle and Hastings, rests on posi- 

 tive evidence, all the others are only supposed to exist owing to 

 the direction of the valleys. I need hardly say that at the pre- 

 sent time, with our greater knowledge of surface- geology, this 

 evidence is quite worthless ; and I feel sure that Mr. Hopkins 

 would not now bring it forward in support of a theory. On the 

 other hand, the longitudinal " lines of elevation '' are observed 

 facts ; but they are nearly all anticlinal and synclinal folds, and 

 indicate compression and not tension. The evidence, therefore, 

 goes to show that this area has not undergone tensiouj and that 

 therefore it has not been raised by the upward pressure of an 

 underlying fluid mass. 



If, now, we attempt an explanation of the structure of this 

 district by means of the Herschel-Babbage theory, we have 

 for our data a thickness of 2100 feet for the Cretaceous for- 

 mation, and 1300 for the Wealden formation, making a total 

 thickness of 3400 feet. The Wealden beds on the anticlinal 

 reach a height of some 800 feet above the sea-level; and to 

 this we must add the thickness of the removed deposits, thus 

 making the original height about 3600 feet above the sea. At 

 London the chalk is about 500 feet below the sea-level ; so that 



