284! Walk from Castleton 



across gneiss, in several places alternaling with felspar-por- 

 phyry, and also traversed by it in the form of veins. 



Walk from Castleton to Spittal ofGlen-Shee and Blair-Gowrie. 



In our walk'from the Castleton to Blair-Gowrie, we travelled 

 parallel with the Clunie water to its source. About five miles 

 and a-half on the way, there is an inn named Newbigging, a 

 convenient halting place for those who may wish to explore the 

 mountains in this quarter. The gneiss, and other primitive 

 slaty rocks, appeared to form the mountains on both sides of the 

 valley. In many places veins of porphyry and granite were 

 observed traversing them, or branches running parallel with the 

 strata thus appearing like beds. At a place named Goats'- 

 craig, we observed a vein of porphyritic granite, 40 feet wide, 

 traversing the strata. In the neighbourhood of the inn the 

 prevailing rocks are quartz-rock, hornblende-slate, hornblende- 

 rock, porphyritic hornblende-rock. Of these, the quartz-rock, 

 with subordinate mica- slate, was the most abundant. Of this 

 rock it may be remarked, that here, as in many other places, it 

 has disseminated through it iron-pyrites, which, by decomposi- 

 tion, communicates to the surface of the rock a yellowish -brown 

 colour. Beds of bluish-grey granular foliated limestone, alter- 

 nating with the other stratified rocks, were observed. All these 

 rocks are more or less intersected and alternated with felspar- 

 porphyry ; and this porphyry, where in contact with the mica- 

 slate, has a blackish colour, and the slate is changed in its nature. 



In our course onward, before reaching the summit of the 

 mountain on which is the water-shed (divortia aquarum) that 

 separates Aberdeenshire from Perthshire, we noticed several 

 beds of bluish-grey granular foliated limestone, with mica-slate, 

 chlorite-slate, and hornblende-rocks, traversed by veins of fel- 

 spar porphyry, and also alternating in beds with that rock. 

 Having reached the highest part of the pass, the line of demar- 

 cation of the two counties, we now descended a rapid acclivity 

 into the valley named Glen-beg. The strata were mica-slate, 

 with the usual SW. and NE. direction. Near the foot of this 

 acclivity we obsened, at a little distance, several large beds of 

 felspar-porphyry, and also of bluish-grey granular foliated lime- 

 stone. The country, which had been hitherto bleak, improved 



