LEWIS. GEOLOGY. 195 



situations elsewhere. I may add that there are two 

 caves containing calcareous stalactites, one near the 

 same point, and the other near Tolsta Head, both of 

 these probably resulting from the vicinity of similar 

 masses of calcareous matter. At Loch Valumis there 

 is also a rock of serpentine containing fine specimens 

 of asbestos, which circumstances did not allow me to 

 investigate accurately. 



The next rock to be described is a conglomerate 

 which is found at Stornoway, forming the point of 

 Arnish and a small island in the harbour, and extending 

 along the eastern shore to a point beyond Gres, where 

 it terminates in the gneiss. It also forms a portion 

 of the Aird, reaching as far as Garbust on the northern^ 

 and the Chicken Head on the southern shore. It here 

 presents perpendicular and very even cliffs, composed 

 of strata inclined at an angle of about thirty de- 

 grees.* It is composed of rolled pebbles of different 

 sizes, reaching to the diameter of a foot or more, and 

 imbedded in a coarse compacted gravel of the same 

 materials; but occasionally it passes into a finer sand- 

 stone. These materials are fragments of quartz, of felspar, 

 and of different varieties of gneiss. 



In its aspect this conglomerate bears a perfect resem- 

 blance to most parts of that great range which is found 

 on the main land of Scotland separating the primary 

 from the secondary strata, but it is in general of a much 

 harder texture. It reposes immediately on the gneiss, 

 and the junction may be seen with great ease between 

 Swordil and the Chicken Head, where it is perfectly 

 laid bare by the exposure of the cliffs. The gneiss is 

 here intersected by granite veins and much disturbed ; 

 in consequence of which, great irregularity occurs in 

 the position, and great inequality in the terminating 



* Caves of various dimensions are found in these cliffs, offering 

 Subjects of considerable beauty to the pencil of the artist. 



