CHAP. XLVI 
THE ACID BOSSES OF SKYE 
385 
pliyre of Beinn 11 a Caillich and. the two Beinn Deargs has invaded on its 
north-eastern side the Cambrian limestone and quartzite, and has truncated the 
sheets oi intrusive dolerite and gabbro that have there been injected into 
them. But to the south-west it rises through the great Strath agglomerate 
already described, and continues in that rock round to the entrance into 
Strath Beg. The eruptive mass is in great part surrounded with a ring of 
agglomerate, as if it had risen up a huge volcanic chimney and solidified 
there, though probably there were more than one vent in this agglomerate 
area. Again the thick mass of agglomerate north of Belig is interposed 
between the bedded lavas and the great granophyre mass which extends 
northwards to Loch Sligachan. On the west side of the Blaven ridge, a 
number of masses of agglomerate are found on both sides of Glen Sligachan, 
along the border of the same great tract of acid rock. 
With regard to the relation of the granophyre of the Bed Hills to the 
great agglomerate of Strath, we may infer that the granophyre has not risen 
Fig. 348. — Section from Beinn Dearg to Beinn an Dubhaich, Skye. 
a a ’ Cambrian limestone ; b b, volcanic agglomerate ; c c c, basalt-dykes older than granophyre : dX, granophyre of 
Benin Dearg ; a-, granophyre m the agglomerate neck ; rf3, granite of Beinn an Dubhaich ; e, basalt-dvke 
younger than granite. 
exactly in the centre of the old funnel, but rather to the north of it, 
unless we suppose, as already suggested, that some of the agglomerate 
belongs to the cone that gathered round the eruptive orifice. It is 
interesting to observe, however, that granophyre, from the same or from 
another centre of protrusion, has likewise risen along the outer or southern 
margin of the agglomerate, generally between that rock and the limestone, 
but sometimes entirely within the agglomerate. The distance between the 
nearest part of this ring of eruptive rock and the edge of the boss of Beinn 
a n Dubhaich is under 400 yards, the intervening space being occupied by 
limestone (or marble), much traversed by north-west basalt-dykes. Most of 
these dykes do not enter the rocks of the vent, and are abruptly truncated 
by the mass of Beinn an Dubhaich. The probable structure of this locality 
is shown in Tig 348. 
The masses of agglomerate which further westward so curiously follow 
the margin of the great granophyre bosses, and those which are entangled 
m that rock and in the gabbro, probably indicate, as already suggested, the 
v°l. 11 2c’ 
