Page:Quarterly Journal of the Geological Society of London, vol. 29.djvu/274

 saw through the northern part of this groove from Callander, and saw from under a roof of gray clouds the ends of distant ridges like blue pyramids against a hard yellow sky. I went down the side of the groove to Stirling, and along it to Edinburgh. There I took rubbings off rocks. I saw that which is better shown upon the inch scale. The large rock-groove is fluted by smaller ridges and furrows. When these are examined on the ground, small ice-marks are found wherever they have not been destroyed. Badges of gravel and of Boulder-clay, whose longest axes correspond to rocky hills of like shape, abound from Strathmore to the Clyde, from the " east neuk " of Fife to the west end of Bute. The Bass, North Berwick Law, Edinburgh, Stirling, Dechmont, Dumbarton, Ailsa, and hills which rise through water and drift all the way to the west of Ireland, are alike in form when they are mapped or seen. Any one can see on this map that which I have seen in travelling about for many years. This big Scotch groove is dug out of a great many kinds of rock, as I believe. The softest are in the deepest hollows, and the hardest are generally highest. Some broad engine has certainly passed over these low lands. The sea has been there ; for shells are in drift. Ice was there; for Bon lder- clay rests upon glaciated rock.

Problems unsolved are, the kind of ice and the extreme size of it, the power which was set to move it, the work which it did, and where and how the work was affected by the material upon which the engine was set to work.

XV. As to the material. — A series of straight parallel ridges are drawn between Callander and Dumbarton, and contrast somewhat with the rest of these forms. At Callander, at Dumbarton, in Arran, in Antrim, and in Donegal are edges of beds of Old Red Sandstone. The ridges drawn on the Scotch map are as the grain in carved wood *. At Slieve Liag is a cross section which shows that these beds have been kneaded and crumpled up edgeways like dough. But the forms shown on the map do but record the relative hardness of denuded beds. In the higher country are a different set of forms. Glen Falloch and Loch Lomond are at right angles to the large groove, and cross the strike of the Old Red Sandstone, and of the older rocks of the central highlands, of Argyll and Berth. The spurs of Beinn Lomond, parallel to the Loch, are long ridges and furrows which cross the strike and the edges of the Old Red Sandstone. Faults, and cracks, and breaks abound in the district; but the Ordnance Map and the country itself do not show them. The Geological Maps do ; but the shapes of Scotland and Ireland do not accord with their numerous faults.

About the head of Glenfalloch, from all the glens and corries about Tigh an Dromma (Bidge House) flow rivulets which go north, south, east, and west through deep glens ; they grow to be rivers, and join the Forth and Clyde, the Tay and the Awe. In each glen is a flat of water-drift fringed on both sides by rows of hillocks of older glacial drift, containing large smoothed stones of many kinds. At the end of each glen are piles of glacial drift in the form of


 * A carved mcdel of the hills about Inveraray was shown.