Page:Journal of botany, British and foreign, Volume 9 (1871).djvu/285

 OVER THE HILLS OF THE NORTH OF ENGLAND. 261

1. The Porphjnlic Hills. — The Cheviot mass, composed tiitircly of iti-iieous rocks of a porphyritic character, situated partly in the north-west of Northuinbeiland, and partly in Roxburghshire. Like all the others, this has its base in Mr. Watson's Alidagrarian zone. There may be a square mile of area that rises into his Arctic zone, the two highest peaks reaching- 2348 and 2676 feet, but the upper part of these peaks is very bare and monotonous, and almost destitute of damp precipice ; and I know of only seven Montane species that grow there above 650 yards. 1 am leaving out of account entirely in this paper that portion of the Cheviot mass that falls within Scotland, which I have not had the oppor- tunity of exploring personally. That portion which falls within Northum- berland is about 2(J0 square miles in area, and is drained by branches of the Tweed and Coquet.

2. The Carboniferous Hilk. — The area which I am including here under this head is that portion of the Pennine chain that falls between the Tyne and the Wharf. It embraces an area of at least a thousand square miles, belongs entirely to the eastern slope of the Pennine ridge, and fills up the whole of the western part of North Yorkshire, Durham, and the southern part of Northuudjerland. The following streams run through it from west to east : — the Wear, Tees, Swale, and Yore ; and the hills between them rise very gradually as we ascend the streams, culminating in several isolated peaks and ridges that reach into the luferarctic, but none into the Midarctic zone. The rocks consist of several important bands of homo- geneous encrinitic limestone, with thick masses of intervening and super- posed clays and sandstone, and in Teesdale a considerable mass of basalt is interposed amongst the sedimentary strata.

3. The Slate Hills of the Westmoreland and Cumberland Lake district occupy an area of about 400 square miles. The main lakes which are in- terspersed amongst them are all decidedly within 100 yards of the sea level. The following peaks exceed 900 yards: — Scawfell Pikes (which reaches 3208 feet), Scawfell, Helvellyn, Faiitield, Skiddaw, Bowfell, Great Gable, Saddleback, Grassmoor, St. Sunday Crag, and High Street. These spread over an area of not less than 20 miles from east to west, and of 10 miles from north to south, and of most of them some at least of the sides are abrupt and precipitous. We may fairly regard all these peaks that have been mentioned as rising into the Midarctic zone ; so that in this point, and also in its much greater rainfall, as well as in its litholo- gical constitution, this group differs from all the other three.

4. The Oolitic Hills of North-East Yorkshire, which, with the Lias upon which they rest, occupy an area of 850 square miles. The Middle Oolite, which, running from east to west, tills up the southern third of this area, is almost entirely calcareous in lithological constitution. The Lower Oolite and Lias of the lower levels and northern two-thirds of the area are arenaceous and aluminaceous. Numerous streams, running prin- cipally north and south, break up the mass, the general character of which is that of an elevated table-land, into dales and glens. None of the higher peaks and ridges exceed 1500 feet, so that this mass is decidedly lower than the three others, and does not anywhere attain even the lufer- arctic zone.

1 am not taking into account at all the low hills of the centre of Norlluunberland, or of the western slope of tlic Pennine chain through (!uud)rrl;Mid and Wesfinorelaml, or its exten-rion through the West itidnig

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