I. — On the Geological Structure of the Wealden District and of the 



Bas Boulonnais. 



By WILLIAM HOPKINS, Esq., M.A., F.R.S., F.G.S. &c. &c. 



[Read February 3rd. 1841.] 



INTRODUCTION. 



Geologists have long recognized the fact of the approximate parallelism of 

 lines of dislocation in those districts in which systems of such lines are found to 

 exist; and in my memoir on Physical Geology, published in vol. vi. part 1. of 

 the Transactions of the Cambridge Philosophical Society, I have shown that such 

 parallehsm would, in many cases and under the most simple and probable con- 

 ditions, be the necessary consequence of the simultaneous action of an elevating- 

 force acting beneath extensive portions of the crust of the globe. I also demon- 

 strated that two systems of parallel dislocations might be produced by the same 

 elevating force, the direction of the one system being perpendicular to that of the 

 other. I also pointed out the circumstances under which, according to theory, 

 there would be a necessary deviation from parallelism in these systems, and I indi- 

 cated the relations which such deviations would bear, in certain general cases, to 

 the boundary of the disturbed district, and to the particular configuration of its 

 surface. On these points I proceeded farther, in theory, than geologists had gone 

 in observation. There are still few districts, even in those countries with which 

 we are geologically best acquainted, where observations have been made in suffi- 

 cient detail to bring this subject, as a branch of descriptive geology, to the point 

 to which 1 have carried it in theory. 



Under these circumstances my attention was directed to the district of the 

 Weald in Kent, Surrey and Sussex, as one in which the phsenomena of elevation 

 might be expected to accord with correct theoretical results in a greater degree 

 than in many other cases, on account of the regularity of its boundary, and the 

 apparent absence of the effects of that more violent, local, or irregular action of 

 the elevating force, which it must ever be impossible to reduce to calculation. 



VOL. VII. SECOND SERIES. B 



