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 

 effluent 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 1 901, 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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