478 
of forming these fissures by a force applied only along one single 
axis of elevation ; whilst the entire series of phenomena 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 the comparison which 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 the Wealden formation to the east 
of Hampshire, near Petersfield, Mr. Hopkins would include also ~ 
(as Dr. Fitton has done in his observations en the Strata of the 
South-East of England) the parallel elevations of Portsdown, the 
Isle of Wight, the Purbeck and Weymouth districts, and the vales 
of Tisbury, Pewsey and Highclere, on the west and north margins 
of Wilts and Hants*. . 
_ Mr. Hopkins has also arrived at similar conclusions respecting 
the longitudinal and transverse fractures which he has investigated 
in the mountain limestone and coal formations of Derbyshire; com- 
mencing, as in the present instance, with a theoretical investigation 
of the mathematical results of expansive forces acting from beneath, 
and comparing these results with observations on the longitudinal 
fissures and transverse fractures examined by himself in Derbyshire, 
and with the answers returned by practical miners in that district 
to a series of printed questions as to facts which theoretical calcula- 
tions had indicated as probable, and which have been fully verified 
by the answers thus obtained. 
In these Memoirs of Mr. Hopkins on the Wealden district, and 
on Derbyshire, we have the first instances of the geological investi- 
gation of any portion of the earth for the express purpose of exem- 
plifying a theory founded on the solution of a mechanical problem ; 
the results he has obtained in the coincidence of the phenomena 
with the mathematical theory by which they have been tested, have 
een remarkably approximate, and make us feel that the time is 
arrived when the investigations of geology have begun to exalt 
themselves beyond the exquisite and delicate investigations of Mi- 
neralogy, and the grand and universal laws of co-existence that give 
dignity and beauty to Paleontology, into those lofty regions of 
General Physics which connect them with the most sublime demon- 
strations of Astronomy. 
It may be seen, by reference to the Ordnance Geological Survey 
of Cornwall, that the elevations and depressions of the older slate 
rocks in the West of England have been attended by numerous 
* 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.— Geol. Trans., 2nd Series, vol. ii. part 2. 1827. 
