[Yn Lioar Manninagh Vol 4 pp16/20]
August 10th, 1901.
LeaderProf. W. Boyd-Dawkins, F.R.S., &c.
This excursion was under the leadership of Prof. Boyd-Dawkins, who had been delivering a series of Field Lectures on Manks Geology, and kindly invited the local Society to attend this excursion in connection with his lecture on the granite and lead mines of Foxdale. Some students from the School of Mines, at Foxdale, joined the party, which consisted altogether of about 40, of whom 15 were members. From St. Johns the Professor led the way through Kenaa, stopping at the top of the lane leading up through the little gill, to deliver the first portion of his Lecture which presented a general view of the Geology of the Island and was illustrated by a map prepared by him. He explained how the general massif of the Island consists of slate with gritstone mixed, formed originally by the mud and the sand deposited as banks in the ancient sea. At Niarbyl the bedding is well marked, the rock consisting of minutely laminated mica and thin laminæ of quartz, in the direction of mica schist. The greater part of the Island is altered slate with mica, known as phyhhite. In process of further alteration small crystals of garnet were formed, as would presently be seen. The slates may be Cambrian, certainly they are not later than Ordovician ; they are identical with those in Cumberland and the Mourne mountains There is no Upper Silurian and no Red Sandstone, for while these formations were being deposited elsewhere this was land. The earliest carboniferous rocks are at Langness in the south, formed of a conglomeration of local rocks. Above this come the carboniferous limestone, dipping seaward, and, on the land side, faulted into the slates by the Port St. Mary fault. On the north side of the Island the red sandstone conglomerates, and breccias, prove to be of Permian age by their identity with these rocks in the Lake country, also faulted into the slates. They extend from the Craig Malin at Peel as far as the north headland of Wills Strand. Along this coastline a perfect section is shown of the various strata which compose it. These represent the newest of the rocks, forming the framework of the Island which appear at the surface. The record, however, is continuous in the north of the Island tinder the great drift deposits extending from Ramsey and Kirk Michael to the Point of Ayre. The borings put down prove the presence not only of carboniferous and Yoredale strata and Permians, but also of Triassic sandstone and red mans, containing valuable beds of salt. All these occur exactly in the same relative position to one another and to the slate as they do in the Lake country. The red marl is undoubtedly continuous underneath the sea level with that of Cheshire and Lancashire on the one hand, and of the district of Belfast on the other.
Before proceeding to the next stopping place, some of the party went to examine three " cairns" in the neigbourhood as marked on the Ordnance Survey. One is now levelled by the plough, but the outline can be clearly traced. Another has been partially opened, displaying a stone cist in the middle, and the third is similar in appearance with a hollow top, but, if there be a cist it is not now visible.
On the way to Old Cornelly Mines an example of garnetiferous slates was inspected, and the leader continued :In this place the slate has been altered into a mica schist, in which garnets occur irregularly scattered. This may have been brought about by the proximity of granite, which does not, however, come to the surface at this place. Whether this be so or not, they are obviously the result of the application of great heat and pressure in presence of water, at a time when the slate was stink to a very great depth below the surface. It must, however, be noted that at the margin of the granite at Foxdale the slates are not altered into mica schist, and they are not garnetiferous.
Proceeding to the celebrated mines the party was met at the Victoria Memorial Clock by Capt. Kitto and Capt. Lean, who conducted them over the surface of the workings, explaining the nature of the work, and of the machinery used.
Capt. Kitto then conducted the party to the site of the ancient graves recently discovered, which he had had re-opened for inspection. This was on the South Barrule farm, just above the cultivated land and by the side of the old road leading to Castletown. Three graves were found side by side, one only half the size of the other two. There was no indication of any enclosure, but the type was distinctly Christian, and the probability is that they formed part of a consecrated burial ground attached to an ancient keeil, the walls and very foundations of which had in the course of time been gradually removed for fencing and other purposes. There still exists amongst the local inhabitants the memory of a keeil in the immediate neighbourhood, and, though a spot further south was pointed out as its site, it seems more likely that this really was its original site.
The Leader now conducted his party to a granite quarry near the washing floors on the slope of Granite mountain (formerly Slieau Ciogh), and pointed out the structure of the granite, and the manner in which it is decomposed. He called attention to the very slight effect it had had on the rock with which it came into contact, a section here showing the slate to be altered not more than about half an inch deep. He pointed out that the blocks of granite imbedded in the drift seen at the quarry formed part of a great series occuring southwards over the Island as far as low water. The distribution of these blocks shows that the ice by which they were transported passed from north to south, the granite occurring in the drit in the Island north of Foxdale being derived in all probability from the highlands of Scotland. He concluded by pointing out that one of the most constant elements in the sea sand is granular quartz which has been derived ultimately from the decomposition of granite.
Capt. and Mrs. Kitto, with their well-known generous hospitality, invited the whole party to grateful rest and refreshment after the fatigue of the day, and after a delightful hour spent in their house and garden, it was with regret that members and their friends once more took the road for a walk to St Johns, and so home by train.