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largest valleys in the Lake District, including the Borrowdale, 
Newlands, and Greta valleys. It receives the overflow of Thirl- 
mere and Derwentwater Lakes, and in its course passes through 
Bassenthwaite Water. 
The underlying rocks of the gathering ground are Skiddaw 
- Slate, the Volcanic Series of Borrowdale, and small patches of Old 
Red Sandstone Conglomerate, and Carboniferous Limestone. 
Perhaps three-fourths of the ground is mountain pasture, and 
one-fourth woodland, arable, and meadow land. A portion of 
sewage gets into the Derwent from the town of Keswick, and from 
villages such as Portinscale, Braithwaite, etc. 
Kerswick.—The Keswick supply is obtained from the southern 
slopes of Skiddaw. The ground is nearly all mountain pasture, 
the substrata being Skiddaw Slate. The water is conveyed one- 
and-a-half miles, by gravitation. 
MiLLom.—This water supply is collected by placing a dam 
across Whicham Beck, which drains the south-eastern flank of 
Whitecombe mountain. The water is not filtered, but screened 
only. The underlying rocks are exclusively Silurian slates, and 
the gathering ground is about four-fifths mountain pasture, and 
one-fifth arable land. The water is brought five-and-a-half miles, 
by gravitation. 
CLEATOR Moor.—The water is collected from the northern and 
eastern flanks of the mountain Dent, contiguous to the Cleator 
Moor district. It is obtained partly from springs, and partly from 
surface water. It is not filtered, but put through fine screens, 
The gathering ground is chiefly mountain pasture, with the excep- 
tion of about one-twentieth part, which is under tillage. The 
substrata are Skiddaw Slate. The reservoir is situated on the 
slope of the mountain, about four hundred and fifty feet above 
sea level, from which the water is conveyed by gravitation. 
ARLECDON.—It is intended to bring the water for this district 
from Cogra valley, situated between Murton Fell, Blake Fell, and 
‘Middle Fell. A reservoir is being constructed, at an elevation of 
