FASSNEY WATER. 103 



of Painshiel, rocks of greywacke are exposed, being arrang- 

 ed in more or less vertical strata. The greywacke varies in 

 mineralogical character from a rock of which the com- 

 pounds are distinct, to one homogeneous throughout ; to 

 determine the true nature of which, if all its relations 

 were not distinctly seen, would be attended with no little 

 difficulty. It has a very dark blackish-brown or bluish- 

 grey colour, a conchoidal fracture, a slight translucency 

 on the edges, and on being struck, emits a highly so- 

 norous sound. Associated with these greywacke strata, 

 near Bull's Leap, felspar occurs, containing a few acicu- 

 lar crystals of augite : it is conformable to the strata which 

 are vertical, but its more immediate relations are not ob- 

 servable. Farther up the stream, and near the junction of 

 the Kilpallet Burn with the Fassney, two dykes of felspar, 

 in some places slightly porphyritic, cross the strata. (PI. 

 XII. Fig. 2.) On the eastern side of the first of these 

 veins the strata dip to the north at about 80°, and on the 

 western side, to the south, at the same angle. At the junc- 

 tion of these rocks, there are appearances the very reverse 

 of induration, inasmuch as both the greywacke and the fel- 

 spar are completely disintegrated. On advancing up the 

 stream other two dykes present themselves, running parallel 

 with the vertical strata ; the first of these is a porphyry with 

 a base of compact felspar, containing crystals of felspar, 



Water is described, by Professor Playfair in his " Illustrations of the 

 Huttonian Theory," as a " true granite.'' If, however, the term "granite" 

 is meant to express a definite mineral aggregate, and is not applied in 

 that vague and general manner in which it has become unfortunately 

 fashionable to use it ; the natural class to which the rock of Fassney be- 

 longs may easily be discovered. By paying little attention to the various 

 marked characters and connexions of the true granites and syenites, the 

 nature of many unstratified rocks has been misunderstood, and to the 

 same inattention we may refer many of those inferences which have, in 

 no inconsiderable degree, affected theoretical geology. 



