Geological Society. 4? 1 9 



the strike of the elevated strata ; and would also be intersected per; 

 pendicularly in the direction of the dip of the strata by many trans- 

 vei-se fissures. In all these fundamental deductions from theory, Mr. 

 Hopkins finds an almost mathematically exact coincidence with ac- 

 tual observation of the longitudinal and transverse fractures in the 

 Weald ; the former are respectively parallel to the strike of the N. 

 and S. Downs which bound the area of the Wealden district, and 

 are convergent to a point near Petersfield ; the latter pervade 

 many minor longitudinal ridges in the same district, and are most 

 obvious in the well-known transverse valleys that intersect at right 

 angles the chalk escarpments of the North and South Downs, form- 

 ing the only outlets of the nine rivers that take their origin within 

 the ellipsoid area of the Weald. 



Many of the minor transverse valleys that intersect the minor lon- 

 gitudinal ridges, give origin to perennial springs, which are thrown 

 out by the dislocation of the strata, where the faults to which these 

 valleys owe their origin intercept the progress of the subterranean 

 waters, by breaking the continuity of the strata they percolate. 



From these fundamental observations, he concludes that the Weal- 

 den district owes its elevation to one simple elementary cause acting 

 simultaneously, and perhaps at successive intervals, at every point 

 within the area in question ; and producing dislocations, not, as 

 some have supposed, along one single central axis of elevation, on 

 the long diameter of the ellipse, but simultaneously on many lines, 

 and causing many minor elevations parallel to the curvatures of the 

 margin of the ellipsoid area in question. 



The theory of the simultaneous action of the moving forces within 

 all parts of the elevated area, does away the mechanical difficulty 

 of forming these fissures by a force applied only along one single 

 axis of elevation ; whilst the entire series of phsenomena accords 

 with the hypothesis of a broad expansive force acting below, not 

 along one single line, but generally and uniformly under the whole 

 district, with equal intensity at every point. 



In this great physical problem, the form of the elevated area is a 

 most important element, and in the case of the Weald, its elliptic 

 form is highly favourable to tlie comparison M'hich has been insti- 

 tuted by Mr. Hopkins : other important elements are the constitu- 

 tion of the strata, their equable thickness, equable cohesion, and 

 the direction of their natural joints. 



In the same simultaneous elevations that have extended from 

 Boulogne through the area of tiie Wealden formation to the east 

 of Hampshire, near Petersfield, Mr. Hopkins would include also 

 (as Dr. Fitton has done in his observations on tlie Strata of the 

 South-East of England) the parallel elevations of Portsdown, the 

 Isle of Wiglit, tlic Purbeck and Weymouth districts, and tiu; vales 

 of Tisbury, Pewsey and Highclere, on the west and north margins 

 of Wilts and Hants*. 



• The term "Valleys of Elevation" was first introduced to English 

 Geology in a paper " On the Valley of Kingsclere and other Valleys," by 

 Dr. Buckland.— Geo/. Tram., 2nd Series, vol. ii, part 2. 1827. 

 2 F2 



