254 
situated at the back of the hills, and in the first trough, the 
rain is 53 inches per annum. Between the Bolton Water- 
works and the Blackburn Waterworks, which have been con- 
structed in the next valley, there is a ridge of high land, but 
under 2,000 feet, and the mean rain at the Blackburn Water- 
works in the second trough, with two ridges of hills interveniug 
between them and the sea to the west, is only 42 inches. 
Further on to the east, the rain diminishes to 30 inches per 
annum. 
The Manchester Waterworks are formed in the long valley 
called Longdendale, running from west to east, being land- 
locked to a great extent at each end. The hills on each side 
of this valley rise to nearly 2,000 feet at their highest 
summits. 
The rain at Manchester in 1859 was 38 inches. At the 
foot of the hills on the westerly side it was 46J inches. At the 
head of the valley, nearly 1,000 feet above the sea on the west 
side, it was 53J inches, and on the east side, just over the 
summit, it was 58^ inches. The land which there intervenes 
between Longdendale and the valley of the Dun rises to a 
height of 1,300 or 1,400 feet. At Penistone, a few miles 
to the east of the hills, the rain was 39 inches. At Sheffield, 
still further to the east, 25 inches, showing that there is a 
constant decrease from west to east. 
Across another portion of the Pennine chain of hills, com- 
monly called the backbone of England, the rain at Rochdale 
in 1848 at the westerly foot of the hills was about 39-^ inches. 
At Whiteholme and at Blackstone Edge toll-bar at the top of 
the hills, about 1,200 feet above the sea, the rain varied from 
66y^- inches to 674 inches. At the easterly foot the rain had 
diminished to 32 J inches, and at York, in the same year, it was 
little more than 20 inches. 
The same results are observed in the mountain ranges which 
surround the Scotch lakes. The mountains here run across 
the line of the prevailing wet winds, and every successive ridge 
and trough or valley to the east shows a diminishing quantity 
of rain. 
Loch Katrine, from which the city of Glasgow is supplied 
with water, is hemmed in by mountains varying from 2,000 to 
3,000 feet in height. 
In 1854, at a rain-gauge at 1,800 feet in height, on the 
slope of Ben Lomond, which rises to 3,192 feet above the mean 
level of the sea, the rain was 109 inches. This rain-gauge was 
placed on a ridge on the westerly side of Loch Ard, which in- 
tervenes between the gauge and Loch Katrine. On the hills 
between Loch Ard and Loch Katrine the rain was 67 inches. 
