Page:Transactions of the Geological Society, 1st series, vol. 4.djvu/104

 sea. It is situated in 55° 32′ N. latitude, and is distant from the coast at Beadnel 19 miles. It commands a noble prospect over the surrounding country, and presents a conspicuous sea-mark to vessels coming across the German ocean. Hedgehope and Harthope are subordinate mountains, and the Flodden Hills on the north-eastern side are a still lower group. The latter descend gradually to Millfield plain, where the primary formation terminates in that direction.

At the foot of the ridge, in some places the usual attendants of primary mountains, the red sandstone and the greywacké slate, are found rising to the day. The former, which bassets out in Roddam Dean, approaches to a conglomerate; the latter, which appears on both sides of Markington burn, is fine grained in structure; but the slates there quarried do not stand the action of the air, The blocks of stone on the summit of Cheviot consist of flesh-coloured felspar porphyry enclosing crystals of reddish white felspar and occasionally minute crystals of hornblende, resembling in this respect the porphyry of Inverary mentioned by Dr. Garnet and St. Fond. Among the rude masses and blocks which lie scattered by the sides of the Wooler-water, porphyry slate, claystone porphyry, porphyritic syenite, granitic syenite, basalt, and coarse red jasper may be recognised, and the Coquet, Aln, Bremish, and Glen abound with agates.

One of the beds which produce the latter mineral is a reddish brown amygdaloid with a basis of wacké, the geodes of which are coated, as usual, with green earth. This rock may be observed in situ on the banks of the Coquet a little above Linn-bridge.

Hornblende rock is by no means uncommon among these hills Housy crag, which rises above the farm house near Langley ford, in the valley between Hedgehope and Cheviot, is composed of a