253 
2,000 feet in height, or on the first or second trough or valley' 
behind such hills and to the eastward of them, is greater than 
in similar hills or troughs to the east. 
Dr. Miller, of Whitehaven, who was a great observer of the 
fall of rain, and to whose researches we are indebted for much 
of what we know of the heavy rainfalls in the Lake District 
of England, concludes from observations that the maximum 
density of the rain cloud is at about 2,000 feet above the sea 
level. That up to this height the rain increases as a general 
rule, and then rapidly decreases as you ascend to a greater 
height. For instance, in twenty-one months the rain, which 
at the coast was between 60 and 70 inches, amounted at 
1,900 feet above the sea to 208 inches, at 2,925 feet it had 
diminished to 137 inches, and at 3,166 feet it had further 
diminished to 128 inches. 
From the observations which he made, it may be inferred, 
as a general conclusion, that the rain will increase as you 
ascend, to about 2,000 feet, and will then decrease; but, 
although this may be a general conclusion, local circumstances 
exercise a very important influence upon the quantity falling. 
It may, therefore, be expected that under ordinary circum- 
stances, apart from, local influences, the greatest fall of rain 
will be on the westerly slopes of mountains which exceed 
2,000 feet in height, and that where the hills do not rise so 
high as 2,000 feet the rain clouds will be driven over, and 
will discharge their watery contents in the first trough, or on 
the easterly sides of the mountains, where they will be pro- 
tected from the winds. Again, such observations would lead 
to the conclusion that in a succession of ridges and valleys 
running from north-west to south-east, and therefore opposing 
themselves abruptly to the prevalent winds which are from 
the south-west, but where the summits are not high enough 
to arrest the progress of the rain cloud, the rain will constantly 
diminish as you proceed to the east. Thus, a ridge exceeding 
2,000 feet high, and so rising above the rain cloud, will have 
comparatively little rain on the east side, while those of a 
lesser height will show that the greatest fall of rain is upon 
the easterly slope. 
Many instances of the truth of these conclusions may be 
adduced. The Liverpool Waterworks are formed upon the 
western slopes of the Rivington Hills, which do not exceed 
some 1,600 or 1,700 feet in height. The Bolton Waterworks 
are in the first trough over these hills. The westerly winds 
impinging upon the hills deposit upon the westerly slopes of 
the hills 484 inches of rain upon ten years J average, while in 
the same time the rain at the Bolton Waterworks, which are 
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