In descending from the Grampians towards the valley of Strathmore, the transition rocks make their appearance. They consist of grey wacke slate, in which the shistose character is more or less distinct, and the imbedded grains of quartz more or less numerous. In this slate numerous elliptical masses of jasper occur, in some cases extending to 30 feet in length, and 10 in breadth. The slate like wise contains nests of slate spar. Compact felspar occurs in beds of considerable magnitude, of a reddish brown co lour, and a conchoidal fracture. Several varieties of trap rocks also present themselves, under the forms of green stone and basalt. Limestone also occurs of a darker co lour, of a less-crystalline structure than the primitive lime stones, and is much traversed by veins of quartz and lime spar. The older members of this formation alternate with the newer portions of the primitive class, and constitute the fundamental rock. of the flcetz class, which we are now to consider.
The fIcetz rocks of this district, although they present great variety of composition, may all be referred to the old red sandstone formation of Werner, as red sandstone is the prevailing rock. The red sandstone is, in some cases, fine grained, and answers for architectural purposes ; and, in other instances, it passes into gra-vc/stone, or a rock composed of water-worn pieces of the more ancient strata, imbedded in a basis of sandstone, or ferruginous clay. The sandstone is frequently in the form of slates, or flags, and is much used for the roofing of houses and pavement. Limestone is likewise common in this district, and in seve ral places is quarried, and burnt for economical purposes. It is commonly in the form of limestone conglomerate, a condition which appears peculiar to the limestones of the old red sandstone formation. Besides these rocks, there are extensive beds of trap, provincially termed seurdie, under the form of greenstone, basalt, amygdaloid, Nvacke, clinkstone, felspar, and porphyry. These rocks are tra versed by veins of limespar and heavy spar, and frequent ly contain traces of copper ores. These flcetz rocks rest upon those of the transition class ; and, at their southern extremity in Fife, support the strata of the coal formation.
The alluvial strata, as may be expected from the varie ty of surface, are very different in appearance and compo sition. On the summit of the Grampians, there is either a light gravelly soil, formed from the decay of the primi tive rocks, or the moisture of the air in those elevated re gions has so far aided the growth of the tribe of plants termed Musci, that extensive strata of peat moss have been formed even on the summit of the highest hills. This
substance is likewise common in the inferior districts, in those places where lakes have formerly existed. As an article of fuel, in a country where there is no coal, it is of first-rate importance. Marl, principally of the kind term ed shell marl, is very common in Angus. It is found in beds under peat moss in old lakes, and is extensively em ployed as a manure. When laid on grass ground, it pro motes the growth of clover, rye grass, and other nourish ing plants ; but when employed as a manure for raising grain, it is found to thicken the husk, of oats in particu lar, in a remarkable degree. The shells in the marl, are those which are still to be found in plenty in the neigh bouring pools and ditches ; Lymnca putris, Planorbis alba, and Cyclas cornea. The prevailing soils are light, gravel ly, and of a red colour. Strong clay soils rarely occur. The soils derived from the trap rocks are usually fertile, of a dark colour, and by some would be termed loam.
There is perhaps no county in Britain, where plants have been investigated with such laborious industry, and such happy success, as the county of Forfar. It was the birth place, and latterly the permanent residence, of the late Mr George Don, whose knowledge of the localities and habits of the plants of Scotland, and of Forfarshire in particular, was never equalled, and who added more new species to the British Flora than any of his botanical predecessors or survivors. From his list of the native plants of Forfar shire, published along with the agricultural survey, where a scientific botanist will find a storehouse of facts, we ex tract the following observations. On the mountains of Clova, the botanist will find a rich harvest of the rarest kinds of alpine plants ; the Saxifraga pcdat?fida, Ranuncu lus alpestris, Eriophorum gracile, Salix rupestris, Hieraci um divaricatum, and Potentilla opaca. Among the crypto gamous plants, he will find the Grinzmia Donniana, (named after Mr Don, who first observed it,) Dicranum pygmeeum, Le cidea funzosa, Ur ceolaria dianzarta. In the lower grounds, he will find the Juncus Forsteri, carinatum, Hyp num crista•castrensis, Riccia fruticulosa, and Jungermannia scalaris. On the sea shore, he will meet with the Elymus arenarius, Carex divisa, flllizmn anoelojzrasunz, Equisetum variegatum.