CHAP. XXXVII 
THE PLA TEA U OF MULL 
213 
The characteristic dicotyledonous leaves at this locality possessed relatively 
large foliage. 1 
To the early observations of Macculloch we are indebted for the record 
of an interesting fact in connection with the vegetation of the land-surface 
over which the first lava-flows spread. He figured a vertical tree trunk, 
imbedded in prismatic basalt, and rightly referred it to some species of fir. 2 
This relic may still be seen under the basalt precipices of Gribon. Mr. 
Gardner found it to be “a large trunk of a coniferous tree, five feet in 
diameter, perhaps Fodocarpus, which has been enveloped, as it stood, in one 
of the flows of trap to the height of 40 feet. Its solidity and girth 
evidently enabled it to resist the fire, but it had decayed before the next flow 
passed over it, for its trunk is a hollow cylinder filled with debris, and lined 
with the charred wood. A limb of another, or perhaps the same tree, is in 
a fissure not far off.” 8 
At different levels in the volcanic series of Mull, beds of lignite and 
even true coal are observable. These seem to be always mere lenticular 
patches, only a few square yards in extent. The best example I have met 
with lies among the basalts near Carsaig. It is in part a black glossy coal, 
and partly dull and shaly. Some years ago it was between two and three 
feet thick, but now, owing to its having been dug away by the shepherds, 
only some six or eight inches are to be seen. It lies between two basalt- 
flows, and rapidly disappears on either side. 
More frequent than these inconstant layers of fossil vegetation are the 
thin partings of tuff and layers of red clay, sometimes containing iron-ore, 
which occur at intervals throughout the series between different flows of 
basalt. But even such intercalations are of trifling thickness, and only of 
limited extent. The magnificent precipices of M'Gorry’s Head and Gribon 
expose a succession of beds of columnar amorphous and amygdaloidal basalt, 
which must attain a thickness of at least 2500 feet, before they are overlain 
by the higher group of pale lavas in Ben More. On the east side of the 
island, thin tuffs and bands of basalt-conglomerate occur on different horizons 
among the bedded basalts, from near the sea-level up to the summit of the 
ridge which culminates in Beinn Meadhon (2087 feet), Dun-da-Ghaoithe 
(2512 feet), and Mainnir-nam-F iadh (2483 feet). Reference has already 
been made to the remarkably coarse character of some of the breccias inter- 
calated among the basalts in this part of Mull, and to the enormous dimen- 
sions of some of the masses of mica-schist and quartzite which have been 
carried up from a depth of 2000 feet or more by volcanic agency (see ante, 
1>. 196, and Fig. 262). 
Above the ordinary compact and amygdaloidal basalt comes the higher 
group of pale lavas already referred to as forming the uppermost part of 
Ben More, whence it stretches continuously along the pointed ridge of 
1 For fuller local details regarding tlie Ardtmi leal-beds, I may refer to tlie original paper by 
the Duke of Argyll (Quart. Jour. Geol. Hoc. vii. p. 89), and to the memoir by Mr. Starkie 
Gardner {op. cit. xliii. (1887), p. 270). 
2 Western Islands, vol. i. p. 568, and plate xxi. Fig. 1. 
8 Quart. Jour. Geol. Soc. xliii. p. 283. 
