JOWETT AND MUFF : GLACIATION OF BRADFORD, ETC. 197 
Valley. The alternation of the harder beds of grit, sand- 
stone, and gannister, with the softer bands of shale, is the 
cause of the terraced features which the hills present. The 
rocks are intersected by numerous faults. 
The general trend of Airedale in this district is from 
north-west to south-east. Actually, the valley makes a 
number of roughly rectangular bends, receiving a large 
tributary valley from the south side at each southern con- 
vexity, viz., the Glusburn Valley at Kildwick, the Worth 
Valley at Keighley, the Harden Valley at Bingley, and the 
Bradford Valley at Shipley. The Worth River itself receives 
two large tributaries, viz., Newsholme Dean Beck on the left 
at Keighley, and Bridgehouse Beck on the right at Oak- 
worth. 
The watershed on the south-west reaches an altitude of 
1,554 feet on Crow Hill. Northwards its altitude falls below 
1,125 feet at the head of the Worth Valley, reaches 1,454 
feet on Combe Hill, and sinks again in a broad depression 
at the head of the Glusburn Valley to below 900 feet. 
A further rise takes place on Thornton Moor (Thornton-in- 
Craven), but does not exceed 1,300 feet. To the south-east 
of Crow Hill the divide gradually decreases in altitude, being 
about 700 feet south of Bradford, and falhng below 450 feet 
south of Leeds. 
The watershed between the basins of the Aire and the 
Wharf e reaches an altitude of 1,323 feet on Rumbles Moor. 
To the north of Silsden it falls to 770 feet and in the 
broad transverse valley east of Rumbles Moor to 450 feet. 
Beyond this transverse valley it rises to 925 feet on Otley 
Chevin, and gradually falls again eastwards. 
III. — The Glacial Deposits. 
The glacial deposits may be conveniently divided for 
the purpose of description into : — 
i. Boulder-clay or till. 
ii. Sand and gravel. 
iii. Unstratified gravelly or clayey material more or 
less intermediate in character between i. and ii. 
