33 
No. II.— EAST SWALE. 
Drainage. — The Wiske rises near Osmotherley, and curves towards the 
west. Near Cowton it receives the drainage of several small lakes, and 
directs its course due south; forming, till its junction with the Swale, the 
boundary between the eastern and western sub-provinces. Below North- 
allerton it receives a small stream, which flows in a south-western direc- 
tion from Hartsey and Brompton. The Codbeck is formed by the union 
of two principal branches. The northern of these rises near Osmotherley, 
and flows past Sigston and Crosby ; the other on the slope of Black Ham- 
bleton, flowing past Kepwick and Borrowby. The united streams wind 
towards the south-east, and receive at Kilvington a rivulet from the vicinity 
of F eliskirk. Passing Thirsk, below Gristh waite they are joined by a con- 
siderable stream, which flows past Boltby and Sutton-under- Whitstonecliff, 
and fall into the Swale below Topcliffe. At Cundall, the Swale receives a 
rivulet on the east, which rises on the southern slope of Hood Hill, and 
runs past Coxwold and Sessay. 
Sureace. — The middle zone includes the summit of drainage between 
the Swale and the Derwent, along Black Hambleton (1246 feet), Kepwick 
Bank (1148 feet), Boltby Scar (1106 feet), Whitstonecliffe (1078 feet), and 
Rolston Scar. The surface sinks into the central vale by a single abrupt 
descent, and the bank is interspersed by several series of irregular cliffs 
and precipices. Below two of these the lower strata have slipped away, 
and lakes have been formed at Gormire and above Kirby Knowle. The 
first of these is about a mile in circumference ; the other is more elevated, 
but considerably smaller. The remainder of the district is all comprised 
in the lower zone. 
Structure. — The surface of the moorlands consist of oolitic strata in 
the form of coralline limestone, calcareous gritstones, and clays. Below 
these extend a series of liassic deposits of varied mineral character, which 
form a broad belt on the east and south of the oolite, extending from Os- 
motherley to the neighbourhood of Northallerton and Thirsk, and touch- 
ing the Swale at Topcliffe. The remainder of the district, like the rest of 
the central vale, is filled up with new red sandstone strata, overlaid with 
boulder (post pliocene) diluvium, 
c 
