THE SALMON 209 
out to sea in hoppers to the amount of many millions of tons 
per annum. The residuum is allowed to flow into the estuary, 
clear and almost scentless. But the process of precipitation 
and deodorisation has removed all oxygen from this effluent, 
thereby rendering it unfit to maintain fish in life. When 
there is plenty of land-water coming down the river, the 
effluent from Barking is carried out to sea, and speedily 
becomes reoxygenated. But in times of drought, when the 
overfall at Teddington Weir falls far short of the minimum of 
200,000,000 gallons a day recommended by Lord Balfour’s 
Commission, the river has no weight to carry out to sea the 
effuent at Barking, which then forms a column of water, 
several miles long, destitute of that oxygen upon which 
animal life depends. This impenetrable column, moving to 
and fro with the tide, effectually bars the river mouth to the 
ascent of salmon until a flood comes to remove it. The 
thermo-bacterial system of sewage treatment, which creates an 
effluent capable of sustaining fish life, is already employed at 
Barking in dealing with a small proportion of London sewage. 
It remains to be seen whether this process can be extended so 
far as to obviate the evil of a deoxygenated outfall. 
Meanwhile, smelts (not to be confounded with salmon 
smolts) have reappeared in the Thames, and have been caught 
in numbers since 1896 as high as Teddington. The smelt is 
a migratory salmonoid fish, spending most of its time in 
estuaries. It is hoped that where they can live and thrive, 
salmon and their young can pass to and fro in their annual 
migrations. Operations on a limited scale have been begun. 
In the spring of 1901, and again in 1902, some thousands of 
smolts, hatched and reared to their second year at Mr. W. 
Gilbey’s fishery at Denham, have been liberated in the Thames, 
and the committee of enthusiasts, with Mr. W. H. Grenfell, 
M.P., at their head, who have undertaken administration of 
the limited funds at their disposal, await developments with 
mingled hope and boding. It is to be feared that, until 
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