POLLUTION OF RIVERS. 39 
salmon ; and, though trade increased before the eyes of the 
people on the surface, the fish below were being gradually 
choked out of existence. 
The extension of the canal system, again, which resulted 
from the success of the Duke of Bridgewater’s celebrated 
canal, led to a considerable extraction of water from the 
natural sources of supply to feed these artificial “cuts,” 
and in this way, again, affected the movements of the fish 
and the still further capacity of the rivers to receive them. 
But still further evils were in store for the salmon. The 
enormous development of mining and manufacturing 
enterprise which this country has witnessed during the last 
hundred years has not only interrupted the free flow of 
water in our rivers, but it has affected their purity ; 
factories and mines multiplying in all directions, and 
requiring large supplies of water, have necessitated new 
weirs for the purpose ; but, not satisfied with this, they have 
returned dirty the water that they took away clean, and 
have sent back poisoned that which they received pure. 
In this way whole watersheds, like those of the Mersey and 
Calder, the Rheidol and Ystwith, the Ebbw and Rhymney, 
have been utterly ruined as fish-bearing streams. Some 
rivers are actually named from the appearance they present 
in consequence of the pollutions that are poured into them. 
The Redbrook, in South Wales, is red with the refuse from 
tinplateworks ; the Blackburn, in Northumberland, is black 
with coal-washings ; the Whitebrook, a tributary of the 
Wye, is white with the refuse chloride of lime from paper 
mills. A man falling into one of the rivers into which 
dyeworks pour their parti-coloured refuse would run a great 
risk of carrying evidence of his mischance about with him 
for weeks in the colour of hisskin. Even where they are not 
thus completely poisoned, the rivers passing through our 
