MINERALOGY. 361 



Observe that the parish of Northma-oen (which was not Mineralogy ©f 

 Yisitcd by Professor Jameson), is bounded toward the Shetland, 

 west by tremendous precipices of granite, similar to what 

 compose Rona's Hills, presenting a strong barrier against 

 the encroachments of the Atlantic ocean. 



Pass Ossa skerries^ lofty insulated rocks, apparently 

 of reddish granite. Pass in a fog the Isle of Yell. Dou- 

 ble Ska.) the most northern point of his Majesty's Euro- 

 pean dominions. It is a small island, composed of 

 gneiss, which forms shores of considerable boldness, and 

 is only at a little distance from the Isle of Unst. An- 

 chor in Balta Sounds Unst. 



The shores around this fine bason are entirely composed 

 of serpentine rock, and the beach is covered with frag- 

 ments of the same. The neighbouring hills, some of 

 which are of considerable height, are also serpentine, and 

 in many places are totally divested of vegetation, (even 

 of lichens), presenting to the wearied eye a naked waste, 

 of an iron-brown colour. The shores, from Balta Sound 

 to Norwick Bay, rise gradually into vast cliffs, all of 

 serpentine, in which are frequently found veins of talc, 

 lamellar actynolite, and common actynolite. Observed , 



imbedded, in one place, a substance very like Labrador 

 Hornblende, but was not able to force out a single good 

 specimen, on account of the hardness of the serpentine 

 matrix. In the bottom of the Bay of Norzcick, the 

 shores are Ioav, and a curious striated micaceous schistus 

 presents itself. The striae are in parallel straight fibres, 

 of a grey colour, with but little lustre, intermixed with 

 small particles of quartz. Near the junction of the ser- 

 pentine and schistus, close by the sea, in a serpentine 

 rock, find fine specimens of talc 4n a vein. This veiu 

 also contained tremolite in quartz. The serpentine 

 hitherto mentioned has an iron-brown colour, from ex- 

 posure to the air ; but the colour of a fresh fracture is 

 generally of a dark-greenish grey. The striated mica- 

 ceous schistus begins in the bottom of the bay, and forms 

 part of the western side of it, rising into lofty cliffs, 

 when it is succeeded by a rock containing large masses of 

 whitish felspar, often crystallized in rude rhomboidal 

 figures. This compound rock is by Mr. Jafmeson called 



gneiss. 



