142 



THE GEOLOGIST. 



who had not then seen the slabs, but only the drawing, and who was of the 

 opinion that they were not organic, Mr. Mac-tie stated that he had no 

 doubt of their organic origin, but was of the opinion that they belonged 

 to a gigantic species of Lingula.* TVhatever they are, I cannot tell, I have 

 simply brought thern 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 Chelcnians have been 

 found in the lowest Silurians of jSTorth 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. 



Granite 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 Red 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 pebbles, in which maybe seen fossils 

 of an undoubtedly Silurian character. Some of these limestone pebbles 

 are several inches in length ; consequently, they could not have beeu 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 wheu it existed as a rough shingle beach. It is therefore probable 

 that the parent rocks of these fossiliferous pebbles once overlaid the pre- 

 sent Cambrian strata. 



2. " On the Edmond's Main Colliery Explosion." By Thomas Farri- 

 mond, Esq. 



* This is scarcely correct. 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 Lingula, 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, 1S63. Unfortunately, I was not able to 

 be present ; but I could not learn from other Fellows who were there that any decided 

 opiuion was expressed about them.— Ed. Geol. 



