to indicate that the grooving agent was deflected from its original course. In the district generally, the uniformity of direction being so great, a mere list of the localities is nearly

all that is requisite.

Arrow No. 15. On the west shoulder of Demyat, three miles from Stirling, 500 feet above the sea, direction ESE.

16. At Torwood, four miles NW. from Falkirk, arrow 16, direction ESE., observed by Sir J. Hall. In this and the preceding, the bearing of the striæ corresponds with that of the upper part of the Frith of Forth, and with the remarkable furrows on the rock of Stirling Castle, of which the figure below is a rough sketch, borrowed from the "Sketch of the Geology of Fife and the Lothians."

This rock forms an isolated hill, rising 300 feet, at S, above the plain which surrounds it. The highest part is an escarpment of trap, a, b, c, d, e, fronting the north-west. The furrow, or rather ravine, dividing the ridge a, from the ridge b, is about 60 feet deep, and sharply cut. The others, between b and c, c and d, d and e, are from 15 to 40 feet, and they all point north-westward. The coincidence in bearing of these furrows with the stria on Demyat, 3 miles northward, and with the others at Torwood (arrow 16) is interesting. 17. On trap, one mile south from Borrowstounness, about 150 or 200 feet above the sea.

18. On sandstone, at Hillhouse Quarry, one mile sou from Linlithgow.

19. On the shore at Granton Pier, nearly one point nort of east-(Dr Fleming).

20. On Corstorphine Hill, nearly one point north of east(Sir J. Hall); also at Ravelston and Craigleith Quarry, see by myself.

21. On the north limb of Arthur Seat, 500 feet above th sea (Dr Fleming); and on the Queen's Drive, south side o the hill.

23. Westward of Craigmillar Castle, exposed in a quarr some years ago.

24, 25, 26. On Pentland Hills. Few groovings have bee found on the Pentland Hills, but those known are interest ing. I found well-marked striæ on the banks of Westwate (arrow 26), about a mile north from Dunsyre, at an elevation of 800 or 900 feet above the sea. The valley, which was not deep, runs south and north, and the striæ crossed it, running exactly east and west. The grooving agent, therefore, did not move downward from the summits of the Pentlands, but crossed one of their southern declivities at an angle of 45°, with the direction of the chain. That agent, therefore, could not be a glacier descending from the Pentlands. Arrow 25 marks the situation of striæ near a place called "Thomson's Wa's," and about 1400 feet above the sea. They were seen by Dr Fleming, who described them as running east and west. On a recent visit to the place, I could not discover a trace of them; owing, no doubt, to the blocks of sandstone on which they were, having been removed in quarrying. They were on or near the ridge which constitutes the watershed, and about half a mile east from East Cairn Hill, whose height is stated to be 1800 feet.

Arrow 26. Very distinct striæ have been recently exposed about half a mile west from Bonally, where a reservoir is now constructing. Mr Leslie, the engineer who planned the works, obligingly called my attention to them. They occur on the north face of Torduff Hill, about 30 or 35 feet above the bottom (the real bottom of rock) of the deep and narrow valley between that hill and Warklaw Hill. The face

of the rock (a felspathic claystone), dips at 40°; the striæ are horizontal, parallel, and quite straight, and extend over a surface from 1 to 3 feet in breadth (vertically), and about 25 feet in length. Their direction corresponds with that of the valley at the place, being precisely ENE. and WSW. The valley is about 300 feet in depth, and, including the upper portion, which curves round the west end of Torduff Hill, about three quarters of a mile in length. It is such a valley as might give birth to a glacier at a glacial epoch. On the top of the same hill, about 900 feet above the sea, striæ and grooves, in short lines, can be detected at intervals, pointing also very uniformly ENE. and WSW. A floating body, such as ice, coming hither from the west, would have a course perfectly unobstructed for 20 miles; for the high ground in a WSW. direction presents the aspect of a plain. Such a body, as it passed along, would graze the western front, the top, and the flanks of this hill; and accordingly we find that, like the hills in the low country, it has the crag-and-tail form, with the crag to the west. Both the head and foot of the hill exhibit proofs of abrasion and grooving, but whether by glacier ice, or floating ice, or both, is still a problem.

27. At Fenton Tower, direction ESE. and WSW., noticed by Sir James Hall.

28, 29. At Old Markle and Gosford Spittle, on the North British Railway, the groovings horizontal, and very distinct, but the surfaces are vertical, they seem to me to give no sure indication of the line of motion.

My principal object in this paper was to register the phenomena observed; and, in speaking of their probable causes, I shall endeavour to be brief.

The Grampian District.-We have seen that, on the east side of this district, at Loch Tay, the abrading and grooving agents moved eastward; that on the west side, at Glen Spean, Loch Leven, and Loch Etive, they moved westward; and that on the south side, at Loch Fine, Loch Eck, Loch Long, and Gareloch, they moved southward. It follows that the nucleus of this physical force, the common centre from which the agents moved, was in the group of mountains extending from Loch Goil northward to Loch Laggan, dividing the VOL. XLVII. NO. XCIII.-JULY 1849.

M

springs of the Spean, the Leven, and the Orchay, from those of the Spey, the Tay, the Earn, and the Forth. And the force must have resided in some substance which admitted of accumulation to a vast extent, for the abrasion produced by it can be traced to the height of more than 2000 feet. Now water could not be so accumulated here except in the form of snow and ice, and even if it were so accumulated in the liquid state, it could not, as has been shewn, produce the effects fairly ascribable to it. These effects are such as cannot be ascribed to any agency known, except that of glaciers, aided perhaps, in some cases, by floating ice.

Professor Forbes, in his paper on the Cuchullin Hills in Skye (in No. 79 of this Journal), describes well-marked groovings on their sides, radiating from the hills in different directions, as from a common centre, so disposed, he observes, that they can be accounted for neither by mountain lakes nor great oceanic waves, nor by any great agent known but glaciers.

I have not yet examined the channels of the Spey, the Findhorn, or the Dee, but I have no doubt that groovings pointing northward and eastward, will be found in them. I infer that the mountainous country, west of the Great Glen, from Morvern northward to Sunderland, was another centre of glacial action; and further, that the Great Glen itself was probably the seat of a glacier which found an exit by its north and south ends, and was fed by the smaller glaciers flowing into it from the east and west.

The striæ, groovings, and kindred phenomena, in the great central valley between the Frith of Forth and the Frith of Clyde, and on the hills contained in it, do not seem to admit of explanation on precisely the same principles. The stria in this district have a direction always approximating to east and west, and there is good evidence to shew that the abrading agent moved eastward. No glacial markings have yet been discovered, so far as I know, running in lines at right angles to the sides of the Pentlands, such as glaciers in the transverse valleys would produce. On the other hand, the striæ found on their summits and flanks (arrows 24, 25, 26), either run along the chain, or hold their course independently of it.

Much remains yet to be done before adequate materials for a satisfactory theory are collected. In the mean time, a few conjectures may be indulged in provisionally.

The transportation of a block of mica slate, weighing 8 or 10 tons, from the Grampians, across the low land, to a point in the Pentlands 1000 feet above the sea, is scarcely susceptible of explanation, except by calling in the agency of ice floating on an ocean at a far higher level than the present. The existence of such an ocean, with masses of ice floating on it, whether in the shape of icebergs, field-ice, or coast-ice, being admitted, it seems a legitimate inference, that the ice, borne eastward by a current, and having probably stones and gravel adhering to it, or imbedded in it, might produce the striæ on the top of Torduff Hill, arrow 24, and those at the other high localities 25 and 26. Farther, as the ocean, in ascending to its higher position, or descending from it, must have assumed different levels in succession, the striæ on Arthur Seat, and Corstorphine and Ravelstone Hills, and at all the other localities, high and low, from Stirling to Gosford and Fenton Tower, might be the result of the same agency. This seems a more reasonable hypothesis than that which assumes, that a vast sheet of ice covered the country from the Grampians to the Lammermuirs (a breadth of 50 miles), and, in moving eastward, grooved both the high lands and the low. It seems to afford a better explanation of the phenomena.

The craig-and-tail form is so often accompanied with groovings, that it is due probably, in a greater degree, to floating masses of ice than to the current which bore them along.

There is a class of phenomena best accounted for by the agency of coast-ice, which is well known to lift stones and gravel from the bottom and sides of rivers and bays, and transport them over moderate distances. Mr Lyell cites examples of blocks weighing 50 tons, being removed in this manner by the ice of the St Lawrence. In this way we may explain such facts as the following. 1. Thousands of granite blocks lifted from the hill in Glen Spean (arrow 1), near Loch Laggan, and carried westward; a vast number of them dropped within a furlong or half a mile of their original site, a smaller number conveyed a mile, and a few to much greater