90 Dr. Mac Culloch's Sketch of the 



the specimens which I have described above. The last specimens 

 in point of structure which I shall notice, consist of radiated me- 

 sotype intermixed with crystals of hornblende, and producing a 

 compound of an unusual appearance. 



The specimens wliich I have now described are almost invari- 

 ably colourless and transparent, or white, but occasionally they 

 assume a brown tinge. One specimen occurred of a sea green 

 hue and of perfect transparency ; but the flesh colour not un- 

 common in this mineral did not fall in my way, although found 

 in the other members of this family which are seen here. 



With respect to the exact locality of this substance, I have only 

 found it at Talisker and at Dunvegan, although it is probable that it 

 exists in many other parts of this very extensive island, which the 

 labour of years would scarcely suffice to examine with the scru- 

 pulosity necessary for this purpose. 



It was at Dunvegan that I observed a solitary crystal of 

 ichthyopthalmite, nor did I succeed in discovering a second. It 

 appears that laumonite has been also found in Sky : in the coursQ 

 of my researches I observed some minute specimens of it asso- 

 ciated with stilbite, but scarcely worthy of notice, unless for this 

 slender record of their habitat. 



Prehnite, a mineral so nearly allied to the zeolites, is also found 

 in Sky, but it is far from common, while the specimens are at the 

 aame time of trifling magnitude. It occurs in the trap at Portree, 

 and at other points along the eastern shore, as well as at Stra- 

 thaird, in the trap veins which traverse the sandstone, as I have 

 already mentioned. On the shores opposite to the point of Clachan 

 in Raasa it is found in a rock, which, although not very common, 

 occurs in different parts of the western islands. This rock is a 

 tompound of augite, glassy felspar, and common felspar, th« 



