142 
THE GEOLOGIST. 
w ]io had not then seen the slabs, but only the drawing, and who was of the 
opinion that they were not organic, Mr. Mackie stated that he had no 
doubt of their organic origin, but was of the opinion that they belonged 
to a gigantic species of Lingula.* "Whatever they are, I cannot tell, I have 
simply brought them before the notice of science, conscious that all traces 
of fossils which are found in the Cambrian beds will receive a careful ex- 
amination. Whether they be actual footprints of some Chelonian, or 
merely imprints, I cannot say ; but impressions of Chelonians have been 
found in the lowest Silurians of North America, and more recently, I be- 
lieve, in Scotland. The outline of these Dalby impressions very much re- 
sembles the dotted outline of the Protichnites, figured in Owen's ' Palae- 
ontology.' " 
Thin veins of Anthracite have been met with at Laxey ; and near to Bal- 
lacraine, a lode of impure graphite, or plumbago, crosses the valley. 
G-ranite comes up to the surface in two distinct places on the island, and 
in both instances emerges from beneath the slate rocks. The first place 
is at South Barool, and the second at Dhoon, about two miles beyond 
Laxey. In both instances it comes up as a huge bulging mass, or boss ; 
in the former place occupying many square acres in extent. Around this 
boss there is a belt of pure white quartz, some score or two of yards wide, 
and containing large flakes of mica interspersed among it. At the junction 
of the clay-slate with the quartz the mica is more abundant, and for a short 
distance a sort of mica-schist passes into the slate-rocks. In the Cambrian 
strata of the island several layers of rock are fine-grained sandstone, as at 
the eastern horn of Douglas Bay, and again at the " Quarter Bridge," 
about two miles from Douglas. It is in the neighbourhoods of the granite 
that the metallic veins and lodes are richest, for at one place the Poxdale 
mines are most profitably worked, and near to the other we have the ex- 
tensive works of the Laxey Mining Company, 
The Cambrian strata in the island bear evidence of extensive denuda- 
tion, for most of the valleys have been formed by the literal scooping out 
of rock ; and it is not unfrequently the case that the hills on each side of 
such valleys may be seen to be the abutments of great arches of strata 
which have once bridged over. 
There is just a glimpse of what this old land may have been composed 
of preserved in the Eed Sandstone conglomerate. At Peel, where this 
conglomerate may be traced resting upon the inclined edges of slates, the 
imbedded pebbles are many of them of quartz, but none of slate ; whilst 
these are accompanied with limestone pehhles, in which may be seen fossils 
of an undoubtedly Silurian character. Some of these limestone pebbles 
are several inches in length ; consequently, they could not have been car- 
ried from a great distance, and the solid rocks whence they were derived 
must have been in the neighbourhood of the conglomerate itself, at the 
time when it existed as a rough shingle beach. It is therefore probable 
that the parent rocks of these fossiliierous pebbles once overlaid the pre- 
sent Cambrian strata. 
2. " On the Edmond's Main Colliery Explosion." By Thomas Farri- 
mond, Esq. 
* This is scarcely con-ect. I noticed the peculiar fibrous structure which appears iu 
the interstices between the cast and the matrix, and suggested, or meant to do no more 
than suggest, that this was possibly fibrous shell-structure, like that of the Liugvila, or 
Pinna. 1 should scarcely like to say I believed in the former existence of a Lingula six 
or eight inches long. I exhibited the specimens kindly sent tome by Mr. Taylor at the 
meeting of the Geological Society, February, 1863. Unfortunately, I was not able to 
be present ; but [ could not learn from other Fellows who were there that any decided 
opinion was expressed about them.— En. Glol. 
