208 BRITISH FRESH-WATER FISHES 



at the end of the eighteenth century ; and second, the 

 inordinate pollution of the tidal part of the river. 



The first of these causes still exists in full force, but there 

 is no reason to doubt that, were salmon to be seen attempting 

 to pass over Teddington Weir, the Conservancy would 

 acknowledge their obligation to erect passes over all such 

 obstacles. This, then, is a remediable difficulty. The second, 

 to those who remember the condition of the river from 

 Chelsea downwards five-and-twenty years ago, might well 

 seem insuperable. The pollution by sewage and refuse of all 

 kinds culminated about the beginning of Queen Victoria's 

 reign in the discharge of the waste from gasworks, and the 

 channel continued to get worse for several years, until all men 

 declared it to be intolerable. The stench from the river along 

 the terrace of the Houses of Parliament was overpowering and 

 nauseating. Below Westminster Bridge a dark, malodorous fluid 

 ran at low tide between exposed flats of black sludge. All that is 

 now changed. By the joint and energetic action of the Thames 

 Conservancy and the London County Council the Thames 

 estuary is as pure as any salmon river need be. Of course the 

 water is turbid, as is always the case in alluvial estuaries, but 

 there is neither organic nor mineral matter in suspension to 

 cause any injury to fish life. I can testify to this from 

 personal inspection of the river from Westminster Bridge to 

 Barking Creek. The black mud flats have disappeared ; the 

 river margin, where clear of buildings, consists of bright flint 

 gravel, clean sand, or ordinary alluvial mud. Why, then, it 

 may be asked, have salmon not returned of their own accord ? 

 The answer is that there is still a formidable obstacle to their 

 entrance from the sea, arising out of the very means which 

 have been adopted to cleanse the river of sewage. London 

 sewage, as is well known, is pumped up at various stations, 

 within the town to such a level as will cause it to flow down 

 to Barking. At Barking it is dealt with by precipitation ; the 

 solid deposit and flocculent matter being removed and carried 



