574 



INTENSITY OF ANCIENT DISLOCATIONS. 



the result of like mutations. Some, however, of these great sedimentary masses, such 

 as the Old and New Red Systems, respectively prove the long continuance of similar 

 conditions, whilst others (as the Oolitic System) bespeak in the varied structure and 

 colour of the deposits, more rapid and frequent changes. 



Combining in our survey then, the whole range of deposits from the most recent to 

 the most ancient group, how striking a succession do they present ! — so various yet so 

 uniform-— so vast yet so connected. 



In thus tracing back to the most remote periods in the physical history of our con- 

 tinents, one system of operations, as the means by which many complex formations have 

 been successively produced, the mind becomes impressed with the singleness of nature's 

 laws; and in this respect, at least, geology is hardly inferior in simplicity to astronomy. 



But to revert for a moment to the phenomena of destruction. Is it possible to con- 

 template the scenes of dislocation, where mountains have been severed, and their 

 parts, once continuous, hurled into distinct ridges, and separated from their parent 

 masses by vast intervals, without feeling astonishment at the intensity of the forces 

 which were employed ? Who can view the promontories and valleys of elevation 

 shattered by great transverse fissures, without wondering at the means employed in 

 their production ? In them, not only have we proofs, that the solid strata have been 

 heaved up on lines both parallel and devious, but also that they have been snapped 

 asunder by numberless rents and cracks, some of which have become deep chasms 

 occupied by rivers. How have the coal-fields been rendered accessible to man's use ? 

 Have we not shown, that many have been forced to the surface by volcanic action, 

 and that some have assumed a basin shape, in consequence of their margins having 

 been thrown into that form by a number of violent upcasts of the subjacent solid masses, 

 which, wrenched from their original position, now converge towards a common centre? 

 Need we recapitulate those curious changes in the lithological character of the deposits 

 effected by igneous action ; or endeavour to rouse the mind to a sense of the greatness 

 of those powers, whatever they may have been, which produced the symmetrical jointed 

 structure of mountains, and carried countless lines of parallel cleavage throughout re-> 

 gions of slaty rocks, in spite, as it were, of the original forms of the strata? 1 



Further, may we not advert to the striking phenomena which portions of this region 

 exhibit, of the complete reversal of a whole range of formations ? Can anything be 

 more startling than the fact, that for many miles the stratified masses have been so com- 

 pletely overturned, that the last accumulated have been placed under those of anterior 

 formation ? Is it not difficult to comprehend how the upheaving force could be so iri- 



1 The observations of Professor Sedgwick on the slaty cleavage of mountains are here alluded to. I may 

 here further observe that Mr. R. W. Fox, of Falmouth, has recently endeavoured to show how parallel lamination 

 (similar to slaty cleavage) may be produced in masses of moistened clay by long- continued weak voltaic action, 

 proving thereby that this remarkable structure cannot be referred to any mechanical cause. (See Report of the 

 Committee, Royal Cornwall Polytechnic Society, 1837.) 



