GLENTILT. 363 



In many of the strata, the mica- slate is coloured 

 with hornblende. Veins of quartz and felspar, 

 every where abound. — Higher up, fragments of 

 sienite and newer granite are found in the debris, 

 along the acclivity on the north side. It is, 

 therefore, not impossible, that an overlying for- 

 mation of these substances may be discovered at 

 the summit of the neighbouring heights. 



But of all the rocks which seem peculiar to 

 Glen-Tilt, the most remarkable is a granular ag- 

 gregate of felspar and hornblende, containing oc- 

 casionally an admixture of quartz : in which 

 $hese ingredients, occurring in grerter or less 

 abunds.nc3, and assuming an endless diversity of 

 proportions^ exhibit the mineral which they com- 

 pose, under many different external aspects of 

 the sienitic and greenstone species. It has, ac- 

 cordingly, from its appearance at some places, 

 been confounded with granite. From this, how- 

 ever, it is completely distinguished, by the pre- 

 sence of hornblende, and the absence of mica ; 

 scales of which so rarely occur, that they can- 

 not be considered as any constituent part of the 

 stone. 



This substance, when we ascend Glen-Tilt, is 

 first observed in thin layers, alternating with stra- 

 ta of micaceous and quartzy rocks, in the bed of 

 the river, a few miles before we reach the Lodge. 

 It afterwards appears in greater abundance, ac- 

 companied still with mica- slate of various as- 



