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EXCURSION XII. 



TO CEJM-NA-CAILLIACH AND THE CASTLES. 



73. EXCURSIONS in Arran may be varied indefinitely 

 according to the taste and objects of the tourist or student. 

 We have indicated a few best fitted to shew the most strik- 

 ing geological features of the island; and as we have now 

 described the different formations and the most remarkable 

 appearances which they exhibit, we shall only mention 

 shortly the chief remaining objects of interest in the northern 

 division, which may be visited in two excursions. We 

 must then carry the student on three excursions two by 

 the South End, and one to King's Cove and the Tor more 

 Stone Circles. 



The principal object in our present excursion will be to 

 look for "the black crystals," as the smoke-quartz crystals 

 found in the granite are called. Their chief repository is 

 the north side of the Suidhi- Fergus ridge and that of the 

 Castles. They are found in the coarse-grained and rapidly 

 disintegrating granite of the great northern ridge. A guide 

 should, if possible, be secured; let him carry a pick-axe to 

 oper up the disintegrating rock; it will also be well to carry 

 a pretty heavy hammer; considerable blocks will then be 

 easily broken. The crystals may also be found by searching 

 the debris, where each little stream, bursting out of the rock, 

 forms a talus on the dispersing of the water. Occasionally 

 beautiful specimens of granite may be found with the in- 

 gredients crystallized. 



The following analysis of the felspar of the coarse granite 

 was kindly made for me by Mr. Magnus M. Tait, in the 

 Laboratory of the College, Glasgow : 



