SANDSTONE OF THE WESTERN COAST. 101 



continuously they have hitherto been found strictly conse- 

 cutive in this respect ; the differences in distant portions 

 arising solely from intermediate flexures or undulations 

 which do not affect this general conclusion. In a few 

 instances nevertheless, a real want of conformity between 

 two approximate portions of secondary strata may be 

 observed ; but the presence of trap in these cases, or the 

 occurrence of other disturbing forces, point out the causes, 

 and show that these irrelative positions have ^eeit the. 

 consequence of changes posterior to their regula'r depo- 

 sition. : 



The same general rule has been supposed to hold among 

 the primary strata, and the present instance therefore 

 affords a striking exception. In the tract under review, it 

 is conspicuously exhibited in the north-west angle of 

 Sutherland ; and the whole of this district indeed presents 

 examples of the conformable and of the unconformable 

 relation borne at the same time by one rock, to those with 

 which it is associated. Whatever light a more extended 

 investigation into the primary rocks may hereafter throw 

 on this subject, it is not at present easy to offer any 

 explanation ; yet it must be remarked that the difficulty, 

 if it be such, is of an artificial nature ; since it is founded 

 on the assumption that all the primary strata, like the 

 secondary, have been formed during one distinct . period 

 of repose in the surface of the earth. It might never- 

 theless be suggested in explanation of the present ano- 

 maly, and without rendering it necessary to disturb this 

 hypothesis, that disturbance and waste combined may 

 have produced the double position of this red sandstone. 

 It has been remarked that in many places the same mass 

 can be continuously traced from a horizontal or slightly 

 inclined, to a vertical position, and it is probable that this 

 change has been effected by posterior derangements. 

 Assuming any given portion of such a mass, it is only 

 necessary to suppose the point of transition removed, and 

 the consequent non-conformity will immediately follow. 



