50 Mr HOPKINS, ON RESEARCHES IN PHYSICAL GEOLOGY. 



above supposed, the principal tension due to it will be in the direc- 

 tion CP, instead of being perpendicular to that line, in which case 

 the deviation in the direction of the fissure will be the contrary of 

 that above represented. 



f Formation of Longitudinal and Transverse Faults — Anticlinal Lines — 

 Longitudinal Valleys — Transverse Valleys — Comparative Effects of 

 subsequent Movements on the Width of Longitudinal and Trans- 

 verse Fissures — Throw of a Vein. 



It appears then, that in the case we have considered, and under 

 the conditions assumed, the elevating forces will produce two systems 

 of fissures with a general approximation (subject to certain modifica- 

 tions) to rectilinearity, and perpendicular to each other. Let us further 

 consider what positions the different portions of the mass may assume 

 subsequently to the formation of these fissures. 



50. The diagram in page 45, represents a transverse section of the 

 elevated range, immediately after the contemporaneous formation of 

 the complete fissures MN, CC, &c. It does not appear probable that 

 the effects of the continued action of the elevatory force will after- 

 wards follow any general law; for the subsequent movements of tlie 

 different portions of the mass, now rendered in some degree indepen- 

 dent of each other by the fissures which separate them, must be con- 

 stantly influenced by that irregularity in the action of the elevatory 

 force, and those accidental and local causes of which it is now impos- 

 sible to form any estimate. If the elevatory force be produced by an 

 expansive vapour, or act through the medium of any fluid, as we have 

 supposed it to do, its intensity must decrease after a certain time, 

 thus causing subsidencies in the elevated mass, the degree of which 

 m different portions will probably be in general determined by acci- 

 dental circumstances. One consequence, however, of these irregular 

 causes, would appear to be necessarily a very general one, viz. a 

 difference of elevation in the adjoining parts of different portions 

 of the mass separated by the fissures, whether longitudinal or trans- 



