CHAPTER XI.

Geological Physiognomy.-Scenery of the Primary Formations; Gneiss, Mica Schist, Quartz Rock.-Of the Secondary; the Chalk Formations, the Colite, the New Red Sandstone, the Coal Measures.-Scenery in the Neighbourhood 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 groupes 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 colouring of the landscape is well nigh as intimately connected with its Geology as the drawing. The traveller passes through a mountainous region of gneiss.

hills, which, though bulky, are shapeless, raise r huge backs so high over the brown dreary moors ch, unvaried by precipice or ravine, stretch away niles from their feet, that even amid the heats of summer the snow gleams in streaks and patches 1 their summits. And yet so vast is their extent base, and their tops so truncated, that they seem half-finished hills notwithstanding,-hills intered somehow in the forming, and the work stopped the upper storeys had been added. He pursues journey, and enters a district of micaceous schist. e hills are no longer truncated or the moors unken; the heavy ground-swell of the former landpe has become a tempestuous sea, agitated by powerwinds and conflicting tides. The picturesque and mewhat fantastic outline is composed of high sharp aks, bold craggy domes, steep broken acclivities, and eply serrated ridges; and the higher hills seem as set round with a frame-work of props and buttresses, at stretch out on every side like the roots of an anent oak. He passes on, and the landscape varies : e surrounding hills, though lofty, pyramidal, and rupt, are less rugged than before; and the ravines, ough still deep and narrow, are walled by ridges no nger serrated and angular, but comparatively rectiliear and smooth. But the vegetation is even more canty than formerly; the steeper slopes are covered ith streams of debris, on which scarce a moss or chen finds root; and the conoidal hills, bare of soil om summit half-way to base, seems so many naked keletons, that speak of the decay and death of nature. All is solitude and sterility. The territory is one of

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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.

And these less rugged formations have also their respective styles,-marred and obliterated often by the Plutonic agency, which imparts to them in some instances its own character, and in some an intermediate one, but in general distinctly marked and easily recognised. The Chalk presents its long inland lines of apparent coast, that send out their rounded headlands, cape beyond cape, into the wooded or corncovered plains below. Here and there, there juts up at the base of the escarpment a white obelisk-like stack; here and there, there opens into the interior a narrow grassy bay, in which noble beeches have cast anchor. There are valleys without streams; and the scene atop is a scene of arid and uneven downs, that seem to rise and fall like the sea after a storm. pass on to the Oolite: the slopes are more gentle, the lines of rising ground less continuous and less coastlike, the valleys have their rivulets, and the undulat

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surface is covered by a richer vegetation. We r on a district of New Red Sandstone. Deep ow ravines intersect elevated platforms. There lines of low precipices so perpendicular and so red they seem as if walled over with new brick; and e and there, amid the speckled and mouldering dstones that gather no covering of lichen, there ads up a huge altar-like mass of lime, mossy and y, as if it represented a remoter antiquity than the ks around it. The Coal Measures present often appearance of vast lakes frozen over during a h wind, partially broken afterwards by a sudden w, and then frozen again. Their shores stand up ound them in the form of ridges and mountainains of the older rocks; and their surfaces are ooved into flat valleys and long lines of elevation. ake as an instance the scenery about Edinburgh. e Ochil Hills and the Grampians form the distant ores of the seeming lake or basin on the one side, Le range of the Lammermuirs and the Pentland coup on the other; the space between is ridged and rrowed in long lines, that run in nearly the same irection from north-east to south-west, as if, when he binding frost was first setting in, the wind had lown from off the northern or southern shore.

But whence these abrupt precipitous hills that stud he landscape, and form, in the immediate neighbourood of the city, its more striking features? They Delong—to return to the illustration of the twice-frozen ake-to the middle period of thaw, when the ice roke up; and, as they are composed chiefly of matter ejected from the abyss, might have characterized

equally any of the other formations. Their very striking forms, however, illustrate happily the operations of the great agencies on which, in the secondary and transition deposits, all the peculiarities of scenery depend. The molten matter from beneath seems to have been injected, in the first instance, through rents and fissures among the carboniferous shales and sandstones of the district, where it lay cooling in its subterranean matrices, in beds and dikes, like metal in the moulds of the founder; and the places which it occupied must have been indicated on the surface but by curves and swellings of the strata. The denuding power then came into operation in the form of tides and currents, and ground down the superincumbent rocks. The injected masses, now cooled and hardened, were laid bare; and the softer framework of the moulds in which they had been cast was washed from their summits and sides, except where long ridges remained attached to them in the lines of the current, as if to indicate the direction in which they had broken its force. Every larger stone in a water-course, after the torrent fed by a thunder-shower has just subsided, shows, on the same principle, its trail of sand and shingle piled up behind it. The outlines of the landscape were modified yet farther by the yielding character of the basement of sandstone or shale on which the Plutonic beds so often rest. The basement crumbled away as the tides and waves broke against it. The injected beds above, undermined in the process, and with a vertical cleavage, induced by their columnar tendency, fell down in masses that left a front perpendicular as a wall. Each bed came thus to present its