LEWIS. GEOLOGY. 191 



because they illustrate practically that irregularity in the 

 apparent position of the beds at the surface* which 

 I have in the next article attempted to explain by a 

 diagram founded on theoretical views.-f- 



Among the very remarkable appearances displayed by 

 the gneiss is the following, of which two examples occurred, 

 one on Bernera isle, the other near Loch Kenhulavig. In 



* PI. xii. % 6. 



f The first is selected to show a remarkable circumstance of frequent 

 occurrence,! namely, the prolongation and compression of the beds; an 

 appearance tending perhaps more strongly than any other of the numerous 

 irregularities which it presents, to prove the soft and ductile state in 

 which this rock has existed. It is to be observed on the island of 

 Great Bernera. The next example is also to be seen in the same 

 island, which offers innumerable contortions of the most fantastical 

 nature; and it almost equally with the former proves the once flexible 

 state of this rock. The third is calculated to show that intricate position 

 of the laminae, with those wavings and deviations, which produce, when 

 only examined at the surface, the apparent irregularity in the position 

 of beds of gneiss, a circumstance to which the diagram above mentioned 

 refers. The present is from one of the shores of Loch Bernera. The 

 fourth is at the Butt of the Lewis, the rock which contains it having the 

 aspect of a piece of marbled paper and being above fifty feet in height. 

 It is principally remarkable for the excess of the contortion. On these 

 representations I must remark, that they are drawn as if on a plane 

 surface, to render those bendings and lines which are perfectly visibla 

 in Nature equally so in the drawing. The hollows, asperities, and 

 projecting fragments, do not prevent that from being quite distinct in 

 the rock itself, which would be obscured in the drawing by the lines 

 and shadows necessary to express these adventitious circumstances. 

 The interlamination of the dark varieties which contain much horn- 

 blende with those which contain little or none, are the lines by which 

 the contortion is rendered visible in the rocks, and the sketches repre- 

 sent the same by the alternations of black and white. The last of 

 these flexures here delineated is to be seen in the cliffs near Loch 

 Hourn on the eastern side, although similar examples occur in various 

 places. Imagination indeed can scarcely conceive an intricacy of this 

 nature of which a resemblance could not be found in Lewis, which 

 far surpasses all the other islands already described in the variety and 

 distinctness of these phenomena. 



PI. xii. fig. 1, 2, 3, 4, 5. 



