300 



E. B. Bailey — The Sgurr of Eigg. 



and more completely vitreous rock, without conspicuous felspar-crystals, which 

 may be taken to represent a more perfectly glassy selvage to the pitchstone 

 sheet. There are also fragments of extraneous origin, which are sometimes 

 rather abundant at the base of the pale band, but become rare towards its top. 

 Excepting at one locality, to be described below, these extraneous fragments 

 are exclusively of basalt and dolerite, evidently picked up from the subjacent 

 rocks. The inclusion of these is not necessarily connected with the brecciation, 

 for they are found also in the base of the pitchstone where it is unbroken and 

 unaltered : for example, in the spur on the north-eastern side of the ridge near 

 Loch na Mna Moire." (Op. cit., p. 47.) 



The exceptional locality reserved in the above account for individual 

 treatment is indicated by Z in Fig. 2. Here the extraneous fragments 

 in the basal pitchstone-breccia include not only basalt and dolerite 

 but also Torridon Sandstone and pieces of silicified wood, one of the 

 latter near the bottom of the layer measuring as much as 8 feet 

 in length. The wood is not nearly so conspicuous, however, as might 

 be imagined from Hugh Miller's allusion to a " prostrate forest ". 



-NVqT- 



'll«-n\rQl\i--J-x-vv 



Fig. 2. The Sgurr of Eigg, seen from the east-south-east, from near Galmis- 

 dale. After Barker [3, p. 46]. 



The lower slopes are of basalt, B, and dolerite, D. The base of the 

 pitchstone, P, weathers into a recess along Y, Z. The pitchstone is 

 intersected by bands of devi trifled pitchstone, which may be described as 

 porphyry or felsite, F. 



It is easy to account for the presence of such additional foreign 

 fragments at this particular point, for the pitchstone-breccia rests 

 here not directly upon the basalt lavas, but upon a definite breccia 

 deposit made up of basalt lavas and Torridon Sandstone, with fairly 

 abundant pieces of Jurassic sandstone and fossil wood.^ Beneath is 

 stratified sandstone with a layer of lignite, and beneath this basalt 

 lavas. 



Per Geikie the breccia deposit and sandstone are the alluvium of 

 the vanished river. For Harker they are an intercalation in the 

 basaltic series. The exposure of the deposit is incomplete, and though 



^ It is by no means certain, however, that the wood in the pitchstone-breccia 

 was not derived directly from growing trees . 



