142 SALMON FOR THE THAMES 



certain estuaries connected with that of the Thames. 

 Probably, in course of years, wandering salmon might 

 stray into the river mouth and work their way up to 

 the first impassable weir ; but why wait for such a slow 

 and fortuitous course of events, if there is reason to 

 hope for success by accelerating the process artificially ? 

 If salmon were reared in considerable numbers and 

 turned into the Thames for three or four consecutive 

 seasons, their well-known homing instinct would 

 prompt them to endeavour to return there after an 

 excursion to the sea. If they did not reappear, it 

 would be fair to conclude that some conditions still 

 prevail unfavourable to their existence; if they did 

 reappear, it would be time to take steps to make the 

 numerous weirs passable to the ascent of breeding 

 fish. 



Still, physical conditions must be fairly faced ; and 

 although there has been a vast improvement of late 

 years in the cleanliness of the estuary, it cannot be 

 denied that a formidable obstacle still exists to the free 

 ascent of salmon. A recent expedition (1899) by river 

 to the lower reaches of the estuary enabled me to realise 

 some truly remarkable results of the joint action of the 

 London County Council and the Thames Conservancy. 

 Those who knew the river below London Bridge 

 ten or fifteen years ago must have a recollection of a 

 malodorous dark current flowing at low tide between 

 exposed flats of black sludge. These flats have dis- 

 appeared ; the margins of the river are everywhere, 



