plateau above 800 yards in elevation, which is not less than a mile across from east to west. Besides this, the Upper zone includes the summit of about a dozen of the peaks that encircle the head of the Wear, beginning with Stangend Rigg and Kilhope Law, just above Allenheads, and curving round by way of the county boundary as far east along the watershed between Wear and Tees as Newbiggin and Swinhope. To get into this Upper zone we have always to rise quite out of the ravines, and there is very little rock within its area, so that the range of variation in plant-stations which it furnishes is very small.
The line of limit between the Middle and Lower zones extends up the College Burn to the farm-houses (Goldscleugh and Dunsdale), at the very foot of Cheviot. The Newton Tors rise distinctly into the Middle zone, but Yevering Bell only just reaches it, and what is called Wooler Common, i.e., the portion of the Cheviot range outside the Common Burn, is all below 300 yards. In the Caldgate ravine the Langlee-ford farm-house, at the foot of Hedgehope, is 250 yards above sea-level. From North Middleton Moor the boundary line between the two lower zones stretches along the steep Cheviot slope above Ilderton, Roddam, Alnham, and Biddleston to Alwinton. The highest point of the range of sandstone hills east of the Till is within a few feet of 350 yards, and the moors north of Rothbury, and east of the hollow between Alwinton and Alnham, reach about the same altitude. North of the Coquet there is a wide extent of high undulated moorland, that forms part of the great Cheviot mass, and begins just over Alwinton; but the 300 yards contour line only touches the stream considerably west of Windyhaugh. Between the Coquet and Reedwater the ridge reaches continuously into the Middle zone from the county boundary to Rothbury, a distance of 20 miles. In the wide tract between the Reedwater and South Tyne the area that reaches into the Middle zone is small. North of the North Tyne it includes the ridge along the county boundary from Carter Fell to the moors above Kielder, with spurs towards the south-east; but between the two branches of the Tyne, the country of the Roman wall and the loughs, only a few of the highest ridges and peaks. But
