34 « 
THE TERTIARY VOLCANOES 
BOOK VIII 
Beinn 11 a Caillich numerous intrusive sheets of gabbro and dolerite traverse 
the quartzite and limestone, and extend down to the sea-margin in the Sound 
of Scalpa. 
There is an important feature in the main gabhro area of Skye not yet 
clearly understood, and which only a minute and patient survey can eluci- 
date. Though I have found among the Cuillin Hills no distinct proof that 
the mass of gabhro ever gave rise to discharges of material, either lava-form 
or fragmentary, which reached the surface, the gabbro area, as already 
remarked, contains unquestionable evidence of explosions and the produc- 
tion of pyroclastic masses. Among the moraine-mounds of Harta Corry, 
blocks of basalt-agglomerate are strewn about, full of angular fragments of 
altered basalt, sometimes highly amygdaloidal, and also boulders in which 
lumps of coarse gabhro are enveloped in a matrix of finer material. I 
did not find the parent rocks from which these glacier-borne masses had 
been derived, hut there can be no doubt that they exist # among the gabbro 
crags that surround that deep glen. Reference has already been made 
to the similar rock found in situ on the opposite side of the Cuillin ridge 
at the head of the great cauldron of Corry na Creich ; likewise to the mass 
of coarse agglomerate which forms a group of knolls and crags on the east 
side of Druim an Eidhne above the head of Glen Sligachan. This rock 
contains abundant blocks of various slaggy lavas like those of the basalt- 
plateau, and runs for some distance along the eastern limit of the gabbro, 
between that rock and the grauophyre. It is intersected by numerous 
basalt-veins. Mr. Harker, as above mentioned, has recently found some 
considerable strips of agglomerate which, like that which I traced round 
the west side of Beinn Dearg, are interposed between the gabbro and the 
bosses of grauophyre, or lie at the base of the volcanic series (p. 284). 
There does not, however, appear to be any evidence to connect these 
isolated masses of agglomerate with the phenomena attending the uprise of 
the gabhro. They seem to he more probably related to the plateau erup- 
tions, and may he compared with those of Strath, Ardnamurchan and Mull 
(pp. 278, 280, 384). That the huge gabbro mass of Skye, besides invading 
and altering the bedded basalts, may have communicated eventually with the 
surface, and have given rise to superficial discharges, is not at all improbable, 
but of any such outflow’s not a vestige appears now to remain. We must 
remember, however, that the gabhro no doubt in many places found its 
readiest upward ascent in vents belonging to the plateau-period, and that 
portions of the agglomerates of these earlier vents may be expected to he 
found involved in it, as the agglomerate of the great vent of Strath has 
been invaded by the grauophyre. 
