CHAP. XXI 
ERUPTIONS IN LORNE 
341 
volcanic hirttory of the Lower Old Red Sandstone period. But no positive 
proof has yet been obtained that any one ol them was the site ot an erup- 
tive vent, and no trace has been detected aronnd them of any lavas or tuffs 
which might have proceeded from them. 
“ THE LAKE OF LOllNE 
The basin of Lome has not yet been carefully examined and described, 
though various writers have referred to different parts of it (Map I.). My 
own observations have been too few to enable me to give an adequate account 
of it. The volcanic sheets of this area form a notable feature in the scenery 
of the 'West Highlands, for they are the materials out of which tlie remark- 
able terraced hills have been carved, which stretch from Loch Melfort to 
IaicIi Creran (Fig. 99), and which reappear in picturesque outliers among 
the mountains traversed by Glen Coe. Between the ancient schists that 
form the foundation-rocks of this district and the base ol the volcanic series, 
lies a group of sedimentary strata which in the western part of the district 
must be 500 feet thick. This group consists of exceedingly coarse breccias 
at the liottom, above which come massive conglomerates, volcanic grits or 
Fig. 99.— View of terraced andesite lulls resting on massive conglomerate, south of Oliau. 
tuffs, fine sandstones and courses of shale. 'While the basement-breccias 
are composed mainly of detritus of the underlying schists, including blocks 
six feet long, they pass up into coarse conglomerates made up almost 
entirely of fragments of different lavas (andesites, diabases, etc.), and more 
than 100 feet thick, which often show little or no trace ot stiatification, 
but break up into large quadrangular Idocks by means of joints which cut 
across the imbedded boulders. These volcanic conglomerates form some ol 
the more conspicuous features of the coast to the south and north of Oban, 
and are well exposed in the Isle of Kerrera. They offer many points of 
resemblance to those of Lake Caledonia, but no certain proof has been 
noted that they belong to the Lower Old Red Sandstone. They have 
oliviously been derived from lava-sheets that were exposed to strong breaker- 
action, which at the same time transported and rounded blocks of grande, 
schist and other crystalline rocks derived from the adjacent hills. During 
