EXPLANATION OF THE PLATES. 



P L A T E 14. 



Tills and the six following- plates are intended to represent some of the most 

 remavkahle circu'.nstances which attend the junctions of the granite with 

 the stratified rocks. They consist of the most interesting portions, and of 

 those which appeared to be the best calculated for explaining- the different 

 appearances which are to be seen at these points. With regard to the 

 method used in sketching them, 1 must add that they are only eye views. 

 Since the greater number of them are represented as if drawn from a point 

 at right angles to the horizon, when they were necessarily taken at an 

 angle often far less than this, it is plain that they will transgress the laws 

 of perspective. But this will produce no alteration in the view they give 



, of the geological facts, however it may derange their graphic accuracy. 

 1 have detailed the portions, most frequently, as if they had been detached, 

 although they form in fact parts of continuous rocks. It is plain, when 

 the magnitude of the objects represented, often extending to 40 or 30 feet, 

 together with the minuteness of the fractures which they exhibit, often 

 descending to the tenth of an incli, is considered, that drawings on so small 

 a scale could not be expected to give {in accurate detail of all the points in 

 such a space. The leading features however have been marked with as 

 much accuracy as the nature of the subject admitted, and whatever omissions 

 or alterations may have been made, no liberties have been taken which 

 could In any respect misrepresent the facts described in the paper and 

 visible in the places noted. 



At the upper end of this figure the granite appears to alternate with the 

 schist, Tracirig it further the true nature of the mixture is evident. The 

 portion was selected to show a fact which has been mistaken for an alter- 

 nation of schist with granite. 



PLATE 15, 



Represents a disturbance produced in the usual continuity of the schist and 

 limestone, the schistose beds being abruptly broken off at their lower end. 

 It also shows the detached points and lines of granite which are described 

 in the paper, the limestone at the same time bearing indications of its 

 original laminated structure, although the bed is not only here in a vertical 

 position, but its course is also at right angles to the ordinary course of tlie 

 beds which constitute the southern side of Glen Tilt. 



PLATE 16, 



Represents the splitting of the limestone bed into three parts, with the intrusion 

 of two masses of granite. A confusion of the granite, scliist and limestone 

 is also visible on one side. It farther represents the flexure of the lime- 

 stone and the red lines of granitic matter running parallel to it, of which 

 detached specimens are in the museum ot the Society. 



