33<3 ON THE HIGHLANDS. 



nature to primitive greenstone. Higher up, the 

 colour of the felspar changes to different varieties 

 of red, and we have porphyritic sienite, with 

 crystals of felspar and scales of mica \ which at 

 length passes into a substance resembling sienite- 

 porphyry, and towards the lower part of the pre- 

 cipice, into felspar-porphyry, or rather, to speak 

 more properly, into porphyritic compact- felspar. 



It is by no means improbable, that in this por- 

 tion of the great formation we are describing, 

 which consists of sienite, simple- granular and 

 porphyritic, the rock at some places, by the dimi- 

 nution of its hornblende, and the addition of quartz 

 to the remaining felspar and mica, may ap- 

 proach the characters of newer granite ; but none 

 of the specimens I was able to procure, entitle 

 me to pronounce with any certainty that this is the 

 fact. The rock described by Mr Williams in his 

 Mineral Kingdom, as the " elegant reddish gra- 

 " nite of Ben-Nevis, and perhaps the most beauti- 

 " ful in the world," appears to be the simple granu- 

 lar-sienite, in which the crystals of felspar are less 

 conspicuous. His porphyry, also, " of a reddish 

 " cast," in which he says, " the pale rose, the blush y 

 " and the yellowish colours are finely blended 

 " through the body of the stone," is the beautiful 

 porphyritic-sienite ; and the " porphyry of a green- 

 " ish colour, with a tinge of brownish-red," which 

 he speaks of* as to be found at about three-fourths 

 of the distance up, seems to be what I have men- 

 tioned as composing the summit of the mountain. 



