420 Geological Society, 



Mr. Hopkins has also arrived at similar conclusions respecting 

 the longitudinal and transverse fractures M'hich he has investigated 

 in the mountain limestone and coal formations of Derbyshire ; com- 

 mencing, as in the present instance, v/itli 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 vith the answers returned by practical miners in that district 

 to a series of printed questions as to facts whicli theoretical calcula- 

 tions had indicated as probable, and M'hich have been fully verified 

 by the answers thus obtained. 



In these IMemoirs 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 tlieory founded on the solution of a mechanical problem; 

 the results he has obtained in the coincidence of the plisenomena 

 with the mathematical theory by which they have been tested, have 

 been 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 Palaeontology, 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 

 parallel fissures and transverse fractures, similar to those in the 

 Weald of Kent and Sussex. In the mining districts of Cornwall, 

 particularly near Redruth, these rents and fissures are known in all 

 their various and curious details, from their having been excavated 

 in search of the metallic ores which they contain. The main direc- 

 tion of these fissures being east and west, they are intersected, like 

 those in the south-east of England, by transverse fractures or cross 

 courses, running nearly north and south. Both these systems in 

 Cornwall obviously result from the same mechanical laws which 

 have not only caused transverse fractures to intersect the longitudi- 

 nal lines of elevation, in the districts of the Weald and Derbyshire, 

 where Mr. Hopkins has demonstrated their accordance with the the- 

 oretical laws of physical induction ; but will be found to have affected 

 every mountain chain produced by angular elevation upon the sur- 

 face of the globe. 



In the Annals of Philosophy, 1821, p. 453, 1 published aMemoiron 

 the Structure of the Alps, in wliich it was shown that all the rivers 

 which descend on the north side of this greatest European moun- 

 tain chain, escape from longitudinal valleys parallel to the general 

 axis of elevation and to the escarpments of the elevated strata, by a 

 series of gorges transversely intersecting these escarpments ; in the 

 same manner as the four gorges, that intersect the Chalk escarp- 

 ment of tiie South Downs, give outlet to four rivers formed in Ion- 



