cally at least, the degrading process is the same as that to which sandstones of a different but equally inferior quality are exposed during severe frosts. In the course of years, however, this sandstone, when employed in building, loses its salt; crust after crust is formed on the surface, and either forced off by the crystals underneath, or washed away by the rains; and then the stone ceases to waste, and gathers on its weathered inequalities a protecting mantle of lichens.* The most valuable quarries in the Old Red System of Scotland yet discovered, are the flagstone quarries of Caithness and Carmylie. The former have been opened in the middle schists of the lower, or Tilestone formation of the system; the latter, as I have had occasion to remark oftener than once, in the Cornstone, or mi 'dle formation. The quarries of both Carmylie and Caithness employ hundreds of workmen, and their flagstones form an article of commerce. The best buildingstone of the north of Scotland best both for beauty and durability is a pure Quartzose Sandstone furnished by the upper beds of the system. These are extensively quarried in Moray, near the village of Burghead, and exported to all parts of the kingdom. The famous obelisk of Forres, so

* When left to time the process is a tedious one, and, ere its accomplishment, the beauty of the masonry is always in some degree de. stroyed. The following passage, from a popular work, points out a mode by which it might possibly be anticipated, and the waste of surface prevented :— " A hall of which the walls were constantly damp. though every means were employed to keep them dry, was about to be pulled down, when M. Schmithall recommended, as a last resource, that the walls should be washed with sulphuric acid, (vitriol.) It was done, and the deliquescent salts being decomposed by acid, the walls dried, and the hall was afterwards free from dampness." - (Recreations in Science.)

interesting to the antiquary-which has been described by some writers as formed of a species of stone unknown in the district, and which, according to a popular tradition, was transported from the Continent-is evidently composed of this Quartzose Sandstone, and must have been dug out of one of the neighboring quarries. And so coherent is its texture, that the storms of, perhaps, ten centuries have failed to obliterate its rude but impressive sculptures.

The limestones of both the upper and lower formations of the system have been wrought in Moray with tolerable success. In both, however, they contain a considerable per centage of siliceous and argillaceous earth. The system, though occupying an intermediate place between two metalliferous deposits, the grauwacke and the carboniferous limestone, has not been found to contain workable veins any where in Britain, and in Scotland no metallic veins of any kind, with the exception of here and there a few slender threads of ironstone, and here and there a few detached crystals of galena. Its wealth consists exclusively in building and paving stone, and in lime. Some of the richest tracts of corn land in the kingdom rest on the Old Red Sandstone the agricultural valley of Strathmore, for instance, and the fertile plains of Easter-Ross: Caithness has also its deep, corn-bearing soils, and Moray has been well known for centuries as the granary of Scotland. But in all these localities the fertility seems derived rather from an intervening subsoil of tenacious diluvial clay, than from the rocks of the system. Wherever the clay is wanting, the soil is barren. In the moor of the Milbuy,- - a tract about fifty square miles in extent, and lying within an hour's walk of the Friths of Cromarty and Beauly, — a thin covering of soil rests on the sandstones of the

lower formation. And so extreme is the barrenness of this moor, that notwithstanding the advantages of its semi-insular situation, it was suffered to lie as an unclaimed common until about twenty-five years ago, when it was parcelled out among the neighboring proprietors.

CHAPTER XI.

Geological Physiognomy. Scenery of the Primary Formations Gneiss, Mica Schist, Quartz Rock. Of the Secondary; the Chalk Formations, the Oolite, the New Red Sandstone, the Coal Measures. - Scenery in the Neighborhood of Edinburgh. - Aspect of the Trap Rocks. — The Disturbing and Denuding Agencies. — Distinctive Features of the Old Red Sandstone. Of the Great Conglomerate. Of the Ichthyolite Beds. - The Burn of Eathie.-The Upper Old Red Sandstones. Scene in Moray.

PHYSIOGNOMY is no idle or doubtful science in connection with Geology. The physiognomy of a country indicates, almost invariably, its geological character. There is scarce a rock among the more ancient groups that does not affect its peculiar form of hill and valley. Each has its style of landscape; and as the vegetation of a district depends often on the nature of the underlying deposits, not only are the main outlines regulated by the mineralogy of the formations which they define, but also in many cases the manner in which these outlines are filled up. The coloring of the landscape is well nigh as intimately connected with its Geology as the drawing. The traveller passes through a mountainous region of gneiss. The hills, which, though bulky, are shapeless, raise their huge backs so high over the brown, dreary moors, which, unvaried by precipice or ravine, stretch away for miles from their feet, that even amid the heats of midsummer the snow gleams in streaks and patches from their summits. And yet so vast is their extent of base, and their tops so truncated, that they seem but half-finished hills notwithstanding-hills interdicted somehow in the forming, and the work stopped ere the upper

stories had been added. He pursues his journey, and enters a district of micaceous schist. The hills are no longer truncated, or the moors unbroken; the heavy ground-swell of the former landscape has become a tempestuous sea, agitated by powerful winds and conflicting tides. The picturesque and somewhat fantastic outline is composed of high, sharp peaks, bold, craggy domes, steep, broken acclivities, and deeply serrated ridges; and the higher hills seem as if set round with a framework of props and buttresses, that stretch out on every side like the roots of an ancient oak. He passes on, and the landscape varies; the surrounding hills, though lofty, pyramidal, and abrupt, are less rugged than before; and the ravines, though still deep and narrow, are walled by ridges no longer serrated and angular, but comparatively rectilinear and smooth. But the vegetation is even more scanty than formerly; the steeper slopes are covered with streams of debris, on which scarce a moss or lichen finds root; and the conoidal hills, bare of soil from their summits half way down, seem so many naked skeletons, that speak of the decay and death of All is solitude and sterility. The territory is one of Quartz rock. Still the traveller passes on: the mountains sink into low swellings; long rectilinear ridges run out towards the distant sea, and terminate in bluff, precipitous headlands. The valleys, soft and pastoral, widen into plains, or incline in long-drawn slopes of gentlest declivity. The streams, hitherto so headlong and broken, linger beside their banks, and then widen into friths and estuaries. The deep soil is covered by a thick mantle of vegetation by forest trees of largest growth, and rich fields of corn; and the solitude of the mountains has given place to a busy population. He has left behind him the primary regions, and entered on one of the secondary districts.

nature.