various parts of Scotland. 423 



As this idea had not suggested itself to me when on the rock, I did 

 not examine, and cannot now recollect, whether it affords situations 

 adapted for the erection of the requisite observatories, a condition 

 without which its other conveniences would be of no avail. 



Devar. 



The beautiful specimens of porphyry taken from this rock may 

 render a short description of the rock itself interesting, and I shall 

 therefore make no apology for occupying the Society a few minutes 

 with an account of it. It is the more worthy of notice, as it is the 

 most accessible, and the best characterized mass of porphyry which 

 I have seen in the various parts of Scotland that I have visited. 

 It is an island and a peninsula alternately, according to the state of 

 the tides, and lies off the harbour of Carapbelltown, which it covers 

 from the south and east winds. It is about half a mile in length, 

 and a quarter in breadth. From the N.W. it rises in a pretty rapid 

 slope, and terminates to the S.E. in a precipitous face, reaching as 

 far as the eye can guess, from one to four hundred feet. It consists 

 of one entire mass of porphyrj^, which however varies much in its 

 colour and texture in different places. It contains no other rock or 

 vein, nor is its contact or connection with any other to be traced, 

 but it appears to extend on all sides below the water. On a first 

 and cursory view, it seems to be formed of upright beds, but a more 

 accurate examination shows that this appearance is a deception, and 

 arises from the tendency which the rock has to split in a vertical 

 direction. Such is its outline and general aspect. that it might at a 

 distance be taken for a mass of trap, similar to those in the vicinity 

 of Edinburgh, its leading features being the abrupt face and perpen- 

 dicular fracture. On examining this great fracture more closely we 



