Ixviii PROCEEDINGS OF THE GEOLOGICAL SOCIETY. 



"I 



undergo in the research of scientific truth. The man who does thus 

 submit to hardships and privations, and almost without an allusion 

 to them by himself, has surely a just claim, on an occasion like the 

 present, to all due praise, not only for the merit of his researches, 

 but also for the modesty with which he has described them. 



It may, perhaps, appear somewhat premature to enter upon any 

 theoretical discussion of the pheenomena of a region with which we 

 are at present so imperfectly acquainted ; but the indications of de- 

 terminate laws in the phsenomena of elevation are so distinct, that 

 what may now be merely matter of inference, will, I doubt not, 

 be hereafter verified as matter of observation. As far as Captain 

 Strachey's observations extended, he found that the directions of all 

 the great longitudinal valleys, faults, anticlinal and synclinal lines, 

 lines of eruptive matter, &c. coincided with the general strike of the 

 beds ; while the transverse valleys coincide equally with the direc- 

 tion of the dip. I need scarcely remind you that this is the law de- 

 duced from the theory which rests on the supposition, as its funda- 

 mental hypothesis, of the simultaneous action of an upheaving force 

 at every point of the area over which the pheenomena of elevation 

 preserve a certain character of continuity. And here I would ob- 

 serve that it is destructive of all just conception of this dynamical 

 theory to suppose the elevating force to have acted along the lines of 

 dislocation, as if distinct forces had been necessary to produce each 

 separate dislocation ; whereas the upheaving force, although it may 

 have acted with different degrees of intensity at different points, is 

 not necessarily assumed to have done so. It may have been, like the 

 pressure of a perfect fluid, equal at every point. Thus the elevated 

 mass, fixed at the horizontal boundary, within which the elevating 

 force is supposed to act, becomes stretched, and is ultimately torn and 

 fissured in those directions in which the tendency thus to tear it 

 is greatest, or rather bears the greatest ratio to the power of resist- 

 ance. It is thus that the complex phsenomena of elevation become 

 referable to a general and simple mechanical cause, and not to a 

 mode of action as complex as the phenomena themselveSj as would 

 be the case if each - particular line of dislocation were due to the 

 action of an especial force along that line. 



The boundary of a district, which is supposed to be thus simul- 

 taneously elevated, is not necessarily defined by those existing phy- 

 sical features which might seem at first sight to define it. Thus, if 

 we take the great ridge of our own country, from Derbyshire to Nor- 

 thumberland, we find that, generally, the country on the lower or 

 western side of the accompanying faults is far more dislocated and 

 disturbed than the elevated or eastern side. In such cases I consider 

 the first movement of disturbance to have been one of elevation, suc- 

 ceeded by an immediate subsidence of the lower side of the district, 

 for want of sufficient .support to maintain it in its more elevated posi- 

 tion. It is in this subsidence that I conceive the effiects of all that 

 lateral crushing to have been produced, which has so frequently 

 given the strata subjected to it vertical or even reversed positions, or 

 folded and crumpled them into such singular contortions ; for it is 



