CHAP. XLIII 
THE GABBRO INTRUSIONS 
333 
ii. RELATIONS OF THE GABBROS TO THE OTHER MEMBERS OF THE 
VOLCANIC SERIES 
Various opinions have been expressed regarding the connection between 
the amorphous eruptive rocks of the hill-groups and the level basalt-sheets 
of the plateaux. Jameson, though he landed at Eudh’ an Dunain, in Skye, 
where this connection can readily be found, does not seem to have made any 
attempt to ascertain it. He noticed that the lower grounds were formed of 
basalt, and that the mountains “ appeared to be wholly composed of syenite 
and hornblende rock, traversed by basalt veins.” 1 Macculloch, in many 
passages of his Western Islands, alludes to the subject as one which he 
knew would interest geologists, but about which he felt that he could give 
no satisfactory information, and with characteristic verbiage he refers to the 
impossibility of determining boundaries, to the transition from one rock into 
another, to the inaccessible nature of the ground, to the almost insuperable 
obstacles that impede examination, to the distance from human habitation, 
and to the stormy climate, — a formidable list of barriers, in presence of 
which he leaves the relative position and age of the rocks unsettled. 2 
Von Oyenhausen and Von Dechen, who wrote so excellent an account of 
their visit to Skye, and who traced much of the boundary-line between the 
gabbros and the other mountainous eruptive masses (“ syenite ”), seem to 
have made no attempt to work out the connection between the former and 
the rest of the volcanic rocks. 3 
J. 1). Forbes, in his able sketch of the Topography and Geology of the 
Cuchullin Hills, was the first to recognize the superposition of the “ hyper- 
sthene rock ” upon the “ common trap rocks ” — that is, the plateau-basalts. 
He was disposed to consider the “ hypersthene mass as a vast bed, thinning 
out both ways, and inclined at a moderate angle towards the S.E.” 4 
Professor Judd regarded the bosses of basic and acid rocks that rise 
out of the bedded basalts as the basal cores of enormously denuded volcanic 
cones. He believed the granitoid rocks to have been first erupted, and 
1 Mineralogical Travels (1813), vol. ii. p. 72. 
2 See Ms Weslcrn Islands, vol. i. pp. 368, 374, 385, 386. With much admiration for the 
insight and zeal, amounting almost to genius, which Macculloch displayed in his work among 
the Western Islands, at a time when, with poor maps and inadequate means of locomotion, 
geological surveying was a more difficult task than it is now, I have found it impossible to follow 
in his footsteps with his descriptions in hand, and not to wish that for his own fame he had been 
content to claim credit only for what he had seen. His actual achievements were enough to 
make the reputation of half a dozen good geologists. It was unfortunate that he did not realize 
how inexhaustible nature is, how impossible it is for one man to see and understand every fact 
even in the little corner of nature which he may claim to have explored. He seems to have had 
a morbid fear lest any one should afterwards discover something he had missed ; he writes 
as if with the object of dissuading men from travelling over his ground, and he indeed tacitly 
lays claim to anything they may ascertain by averring that those who may follow him “ will 
find a great deal that is not here described, although little that has not been examined ” (p. 
373). Principal Forbes long ago exjjosed this weak side of Macculloch and his work ( Edin . New 
Phil. Journ. xl. 1846, p. 82). 
3 Karsten’s Archiv, i. p. 99. They frankly admit that “the relation of the hypersthene 
rock to the other trap rocks was not ascertained.” 
4 Edin. New Phil. Journ. xl. (1846), pp. 85, 86. 
