Page:Transactions of the Natural History Society of Northumberland, Durham, and Newcastle-upon-Tyne (1867).djvu/111

Rh most striking feature is the basaltic dike, which in some places reaches a height of 700 or 800 feet above sea-level, forming a decided ridge across the moor from west to east, with an escarpment towards the north which, in several places, consists of a cliff 20 or 30 feet in depth, as at Kyloe, with great heaps of angular slate-coloured basaltic debris scattered over the embankment below it. For several miles along the top of this ridge, with nothing on either side but heathery moor, the Roman wall is carried, following the irregularities of the ridge with pertinacious adherence. Rising from the Black Burn west of Featherstone Castle, where the water, after running for some distance in a deep and narrow channel is thrown over a columnar cliff in a succession of falls, from which the broken sedimentary rocks dip at every angle, and from the wild ravines called the Nine Nicks of Thirwell, between the Tipple and Haltwhistle Burns, the ridge forms Wall Town Crags and Cockmount, and thence sweeps with a slight tendency towards the north by way of Sewing Shields, Black Bank, and Crag Lough, in the direction of Wall and Gunnerton. Crag Lough is a tarn half a mile in length, with a fine cliff of the kind just alluded to rising up from the water's edge on the south side. Muckle Moss is a large swamp upon the hill slope 2 miles to the south-east, which is well-known as a botanical station. By means of the Newcastle and Carlisle Railway this tract is all brought within the compass of a day's excursion from Newcastle. Round the head of the two branches of the Allen for 10 miles a continuous ridge of high heathery fell forms the watershed between Tyne, Wear, and Derwent. The highest points are near the centre—Kilhope Law, 2206 feet, and Stangend Rigg, 2074 feet; but for the whole 10 miles the ridge scarcely sinks below 1700 feet, and the spurs in a northern direction maintain a sufficient height for several miles to give East and West Allendale more of a decided dale character than any other of the Northumbrian valleys. This is well known as a rich mining tract. The limestone is thrown down to the level of the river in the western, and below the level in the eastern hollow in the upper part, so that the higher reaches of the main streams have very little to diversify them, and the hills are