[From Vannin Lior (Yn Lioar Manninagh) Vol 1 No 1 pp77/80]

THE ASPECTS OF THE "CRAGS" OF THE MANX MOUNTAINS IN RELATION TO THE GLACIATION OF THE ISLAND.

DR HAVILAND. (Read April 1st, 1886.)

In my first Paper on "The Isle of Man and the Glacial Period" I mentioned having discovered a remarkable boulder on the south-east side of Greeba, on the east side of the mountain as regards the course of the mer-de-glace from Ireland and the North Channel. On this side I noticed that Greeba (1,380ft.) is rugged and cuff-like, whereas on the side exposed to the ice-flow, it is smooth and mammated. Since then I have examined many of the heights, especially those north of the central valley, and have found that nearly all the mountains bear traces more or less discernable of similar action, so that, in the Paper which I had the honour and pleasure of reading before your Society at Castletown in February last, I felt justified in stating, that whilst your rounded fells tell us plainly how they have been sculptured, some are capable of giving further evidence, viz., whence the sculptor, ice, came.

Situated as is the Isle of Man, in medio, as Julius Caesar described it, between Ireland and Great Britain, it occupies a position which is unique as regards the advantages it offers to the glacialist for the study of the march of those mighty glacier contingents that swooped southwards from Scandinavia, Cumbria, Scotland, and Ireland, to unite in one vast mer-de-glace, the special mission of which seems to have been the grinding down of sterile rocks into fertile soil, and making fruitful many lands, like your own, that otherwise would have remained unblessed either with the waving corn, the green pasture, or well-laden orchards. Such an epoch in the world's history deserves consideration, and especially at the hands of the geologist, whose knowledge is day by day growing more and more useful to the agriculturist, the engineer, the miner, the architect, and to innumerable other labourers, amongst whom the medical worker is not the least grateful.

The Isle of Man affords, as I have already said, advantages for the study of this grand epoch, which few localities, if any, within the circuit of the British Isles can equal, much less surpass; it behoves all, therefore, who would unravel the many mysteries connected with the course of this great ice age, to note what is around them, for every well ascertained fact is a rung-rise in that ladder of knowledge which we must ascend if we desire to extend our historical horizon of this grand and eventful epoch.

The local glaciation of the Isle of Man is surpassed in interest by the important office the Island fulfilled of recording the events which took place around it during those long continued con tentions that obtained between the several glacier-contingents that poured out from the innumerable mountain valleys that abound from Norway to Ireland.

Eminently neutral during the whole of this grand struggle, and adding little or nothing that would either favour or damage the success of those great ice contingents that pressed around it, it still kept records of many great events, when its mountains, its glens, or its coasts were the scene of contention, for their records are to be found even now, like the relics on an historical battlefield, which the plough turns up in the furrow — granite from Scotland, iron-stone and coal from Cumberland, flint and chalk from Ireland — all telling how the tide of victory ebbed and flowed ; how one contingent prevailed, left its spoil behind, to be succeeded by one still stronger, which in its turn was turned aside, leaving evidence of the country whence it had set forth — so that in the end this little Isle was left encumbered, to its advantage, however, with the spoils from many countries, for they now cover its plains and valleys with a fertile soil in which agriculture rejoices ; and many an enduring portrait in the profile of your scenery, and many an imperishable engraving on rock and boulder sculptured on it, from which geology will learn how to write the history of those events which have both beautified and fertilised your country.

The last great ice-age was not the only one probably which sculptured your Island. It is now held that many of the formations from the carboniferous limestone upwards to the Norfolk crag, give evidence of former glacial periods. Cumming was one of the first to assert this from boulders which he found in the old red conglomerate in the south of the Island. Since then much evidence has been added, and Professor James Geikie gives a most interesting list of formations in which evidence more or less conclusive of former glacial epochs has been found. If the Isle of Man had been submerged, like some other parts of the British Isles, during the deposit of those formations which characterise many parts of England, Scotland, and Ireland since the limestone period, it would have shared these deposits, and if it ever was so submerged, and these deposits did ever exist upon it, then they must have been denuded off, for not a trace now remains as evidence of their existence. It is more probable, however, that, through long ages, especially during the secondary and tertiary periods, no submergence whatever took place. We, therefore, must conclude, if it had, during the millions of years involved, been an island, it must have been subjected to those glacial periods, traces of which have been found in later English, Scotch, and Irish formations, Still it is quite within the range of possibility that it was once covered with coal-bearing formations, and red sandstone, lias, oolite, chalk, &c., and that all these have been annihilated by denuding agents. However, on this I will not venture to speculate, but content myself with now drawing your attention to some of the few facts in the profiles of your mountains which I think well worthy of your consideration in studying the glaciation of the Isle of Man, and endeavouring to understand the origin of some of the softened features in the Manx scenery.

The diagram which I have prepared to illustrate this Paper, shows vertical sections of four mountains familiar to you all; two of them being close to your neighbourhood. They are drawn on a horizontal scale of six inches to the mile, and on a vertical one of 300ft. to the inch. The mountains selected are Greeba, Mount Karrin, Snaefell, and North Barrule; I will begin with Greeba, as it illustrates remarkably well the features to which I direct your attention.

The sky-line of this mountain in the diagram is supposed to extend from about 34 miles to the N.W. of its summit at an elevation about 113ft. above sea level; crossing, in an east-south-easterly dicection, Glen Helen, 300ft. to the N.E. of Beary Park, then ascending to 975ft., where it meets with the sources of Greeba River, and thence to the summit, where, at the pile of stones, it reaches 1,382ft., aad then suddenly descends to 1,076ft. at Creg-ny-Greeba; this "Crag" or Creg has a south-easterly aspect, and presents a remarkable appearance, interesting alike to the artist and geologist. I have continued the line through the ordnance levels of 345ft., and 376ft. to the Peel and Douglas road, which at the point of crossing is 105ft. above sea-level, across Union Mills, the River Dhoo, Kirby Lodge, 70ft., the Rivers Dhoo and Douglas 36ft., to near the Carnane, Nunnery Howe, at the feet level, where this bold height suddenly at 242ft. descends to the sea at the mouth of the Pigeon Stream; a total distance of 9¼ miles. Throughout its entire length, this line is full of interest and instruction, but I must limit myself to its first period. From its commencement to the summit the eye is at once struck with the softened mammated undulations from the extreme N.W. point to the summit of Greeba, as if the original heights had been smoothed and rounded by some mighty power having a direction towards the S.E. from the N.W. sea. At this point the mountain offered no further resistance, and the agent in the form of the great ice-sheet with its marvellous spoils of fill, or ground moraine, laden with rock boulders from distant lands, fell over the pre-glacial crags of Greeba, depositing some of them at their feet and under their protection, others over its further course across the great central valley and over Nunnery Howe, until it gained the leeward side of that height, which is now sea, but which was then filled with ice belonging either to the foremost part of the same contingent from the N.W. that we have just followed, or which had originated in the glaciers of the mountain valleys of Cumberland or Scotland. In a previous Paper I have described the force brought to bear on elevated land during the passage of the irresistible ice-cap, thousands of feet in thickness, and endowed with a rasping foot beset with the hardest rocks firmly set in its ice-grip. Greeba has afforded us a typical illustration of the sculpturing powers of ice; let me now briefly point out where other similar evidences of the same phenomena are to be found.

The next section passes from high water mark on the N.W. coast of Ballaugh to high water mark to the N.E. of Laxey Head, a total distance of ten miles from N.E.to S.E. This sky-line carries the eye just over the fringeing coastal barrier of post-glacial deposits that once encircled the lakes which characterised the Curragh (113ft.), thence across the beautiful Ravensdale brook and valley to upwards of 975ft. on the ridge of Mount Karrin, whence it precipitately descends to Craig Moar, so called from the "crags" which here have a south-easterly aspect, and overhang the left bank of Sulby River as it flows over its many-bouldered bed in Sulby Glen, about 340ft. above sea level; about one and a half miles from this spot in the same direction the line crosses Snaefell (2,034ft.) and descends abruptly until the "crags" are reached at a height of 1,703ft., these have a S.E. by E. aspect ; we continue on the same course, crossing streams, until Creg Agneash (658ft.) is reached, overlooking Glen Agneash and Glen Drink, passing other streams before crossing the Ramsey and Douglas road, after which it descends abruptly to the high-water mark at the foot of the cliffs, having a south-easterly aspect, to the N.E. of Laxey Head. Here, again we find a repetition of the same features that characterised the Greeba section, smooth and rounded to the N.W., whilst the "crags'" to the leeward of the ice-course have south south-easterly aspects.

Let me now give you my last illustration, taken from the heights which form the back ground to Ramsey (the old Norse town Ramsaa, or Hrafens-aa). This section extends from high water on the N.W. coast of Jurby (Jorabyr) to the same level at Port Korna,.on the S.E. coast of Maughold (S. Machuti), and has a total length of 10½ miles. This line crosses the embankment of the post-glacial lake district in the north, where it is 86ft. high, then descends to the Curragh, until it meets with the Sulby River, where it is about 40ft. above sea level, within half-a-mile of which it rises to 433ft., after which it gains the ridge of Sky Hill, at 700flt., and then suddenly descends over the "crags," having a south-easterly aspect at a height of about 200ft. above the left bank of Glen Auldyn River, across which it passes to ascend North Barrule (1,840ft.), where it descends abruptly over the "crags" to the S.E. of that mountain, from thence it makes precipitate descent into the weird and desolate valley through which the Corrony mountain torrent tumultuously rushes (375ft.) before it enters the lovely Glen of Rhenab and bounds over still lower "crags" as a graceful waterfall, amidst mosses, ferns, and foliage of varied beauty, from which it at last finds its way to the sea shore between the cliffs of Port Korna, on the S.E. coast of Maughold,