" Researches in Physical Geology." 5 



I am not duly qualified to offer an opinion concerning the 

 mathematical portion of Mr. Hopkins's work : but, admit- 

 ting the great merit of the application of his propositions in 

 pointing out what state of things is, or is not, compatible with 

 the action of an elevatory force, I would venture to offer some 

 remarks respecting the accuracy of the data on which his 

 reasoning is founded. And I the more readily enter on this 

 examination, as he has stated that his " speculations are 

 thrown out with the hope of indicating some of the more cri- 

 tical points of inquiry on which the ultimate determination of 

 this question must turn, and which are generally best indi- 

 cated in such cases by theoretical discussion." 



I have, in my " Treatise on Primary Geology," expressed 

 an opinion that many supposed cases of elevation may be ex- 

 plained by the lines of structure, and by depositions on un- 

 even surfaces; but waiving this at present, I will at once 

 proceed to consider the nature of the elevatory force and 

 its modes of action, adopted by Mr. Hopkins as the basis of 

 his investigations. 



The elevatory force which acted upon the lower surface of 

 the uplifted mass is supposed to have been some expansive 

 fluid. Now until the mass be ruptured this may be a satis- 

 factory cause ; but is it not probable that immediately the re- 

 sistance has been overcome by the production of fissures, an 

 explosion would follow, which would be as much more ter- 

 rific in its devastations than modern volcanos, as the vent, ex- 

 tending across whole continents, would vastly exceed the di- 

 mensions of a crater ? Can the present state of things — strata 

 dipping on either side of mountain ranges traversed and in- 

 tersected by regular systems of veins and dykes — be supposed 

 to have resulted from such tremendous convulsions ? And 

 again, the internal pressure being removed by the rupture of 

 the elevated mass, and the support consequendy withdrawn, 

 ought not the strata to have fallen down and have obliterated 

 the spaces in which the veins and ranges of granite are said 

 to have been subsequently formed? 



This objection might be, in some measure, got over by sup- 

 posing the uplifted and fissured mass to have been acted on 

 whilst a solid layer was interposed between it and the moving 

 power, whereby the fractured strata would be supported; 

 but such an expedient, even if admissible, would only be an 

 imaginary solution of the difficulty, and would be at variance 

 with Mr. Hopkins's deduction that the fissures must neces- 

 sarily commence in the imdei- part of the mass. 



Granting, however, the probability of tiiis modus operandi, 

 and the accuracy of \\wjirst upproxiination, we will proceed to 



