AHRAN. GEOLOGY. SECONDARY STRATA. 385 



elevated position, as in all other situations where they 

 approach the granite. This remark must already have 

 suggested itself to the reader ; but as this appearance 

 involves some important questions, I shall dwell a 

 little more largely on it, and proceed to consider how 

 far many of the remarkable circumstances that have 

 passed under review involve questions of general interest 

 in geological science. 



It has been shown that in all those parts of Arran 

 which are remote from the granite mountains, the 

 secondary strata occupy a position, either horizontal, 

 or little deviating from that ; if we except a few very 

 local and limited disturbances which occur in the vicinity 

 of certain rocks of trap and of the other analogous 

 substances. But where the same strata approach the 

 granite, they are in a certain degree adapted to its 

 general outline ; being elevated at angles, often of 

 considerable inclination, and incurvated to suit the 

 forms of that rock, or those of the primary strata which 

 are interposed. It has also been shown that the ten- 

 dency, as well as the quantity of the dip, bears a 

 relation to the form and position of the mountains ; 

 the whole marking the general adaptation of the secon- 

 dary strata to the basis on which they repose. It will 

 naturally be asked, whether these strata were deposited 

 in the position which they at present occupy, or whether 

 that has been altered in consequence of subsequent 

 changes in their foundation. The phenomena to be 

 witnessed in numerous alluvial deposits, show that stra- 

 tification is not necessarily limited to a horizontal plane ; 

 but that a regular succession of substances can be de- 

 posited in beds, on planes of considerable inclination. 

 But this argument does not apply to the strata under 

 consideration. The necessary position of an empty shell 

 of a certain concavity subsiding in water, is sufficient 

 to determine the original position of the stratum in 

 which it lies ; and it has been shown, that in different 

 VOL. ii. c c 



