20 
been called “ Yoredale limestones,” from their abundant developement 
here. A narrow ridge of magnesian limestone borders the millstone grit 
at Tanfield and Shape. The remainder of the district is included in the 
great central vale. 
No. VI.— NIDD AND WHABFE. 
Dra.ina.ge. — The Ainsty is a highly populated and richly cultivated 
district, only 82 miles in superficial area, bounded on three sides by the 
rivers Nidd, Wharfe, and Ouse, and on the west by a line drawn from 
Colthorpe to Thorpe Arch. The southern portion is drained by a small 
stream, the two branches of which rise near Wighill and Marston. It 
flows towards the south-east and falls into the Wharfe, near Bolton 
Percy. On the north, also, a rivulet rises-near Bilton, and falls into the 
Ouse opposite Overton. 
Surface. — The surface is very little undulated or elevated; so that no 
portion of the district rises above the isothermal line of 48 degees. Near 
Askham are a series of low wooded bogs, which produce in abundance 
the very local Carex paradoxa. 
Structure. — The surface of nearly the whole of the district, like that of 
the remainder of the great central vale, consists of new red sandstone 
strata, overlaid with diluvial deposits. A narrow terrace of magnesian 
limestone bounds them on the west, and margins with cliffs that portion 
of the rivers. 
No. V.— EAST TEES. 
Drainage. — From the southern bend of the Tees below Darlington, it 
flows with many windings in a north-eastern direction, past the towns of 
Yarm and Stockton, and expands into an estuary at Middlesborough. 
The ballast hills around its mouth afford an interesting ground for the 
botanist, as they produce several species which have originally been in- 
troduced from the south of England, or the Continent. The marshes in 
the neighbourhood of Coatham and Bedcar are intersected by numerous 
salt water ditches, (locally called stells,) which supply various maritime 
rarities. The Leven is formed by the union of two branches, which unite 
near the town of Stokesley. The northern of these rises near Codhill, 
