194 LEWIS. GEOLOGY. 



its ordinary degree of softness and its fissile disposition. 

 I need not repeat the general remarks formerly made on 

 this transition ; the recurrence of other similar instances 

 serves to prove that it is an appearance of no accidental 

 nature or limited extent.* 



This rock occupies a very considerable tract in Lewis, 

 occurring on various parts of the coast from Storno- 

 way southwards. Were it possible to have access to the 

 inland rocks in this quarter, there is little doubt that 

 it would be found to extend very far within the country, 

 here as well as at Stornoway. From Loch Shell to Loch 

 Brolum it forms the whole range of cliffs, being mixed 

 in an irregular manner with the common gneiss, and 

 traversed, as that is, by granite veins. It is much con- 

 torted and displaced, being also broken into arches and 

 hollowed into caves, the higher pinnacles being the resort of 

 the eagles with which this shore abounds. At Loch Brolum 

 this mixed rock is gradually succeeded by a simple argil- 

 laceous schist, the gneiss being at length totally excluded. 

 It here contains green compact felspar, and resembles 

 precisely that soft schist which occurs at the entrance 

 of Loch Maddy. Beyond this point I observed it no 

 longer, the gneiss in its most common forms returning 

 at Loch Valumis and continuing to the entrance of Loch 

 Seaforth, where the coast line of the Lewis terminates. 



I observed but few of those minor beds of the rocks 

 which are of general occurrence in gneiss, and of which 

 examples have been described in the other islands before 

 examined. A body of limestone occurs at Gres, near the 

 junction of the gneiss with the conglomerate to be hereafter 

 described. It is however not easily examined, and it 

 will probably be found to appertain to the red sandstone, 

 since it is known to form partial deposits in similar 



* Since the period at which this was written I have often met with 

 argillaceous schist connected in the same manner with gneiss, and 

 occupying tracts of various extent. It occurs thus in Sutherland, in 

 Ross-shire, and clse\\hcrc on the western coast of the mainland. 1818. 



