204 SALMONIA. 



where marl or loam is mixed with gravel ; 

 and they are not found abundant except in 

 rivers that have these characters. It is im- 

 possible to have a more perfect specimen of 

 a grayling river than that now running before 

 us, in this part of its course. You see a suc- 

 cession of deep still pools under shady banks 

 of marl, with gentle rapids above, and a long 

 shelving tail where the fish sport and feed. 

 Should there be no such pools in a river, 

 grayling would remain, provided the water 

 was clear, and would breed ; but they cannot 

 stem rapid streams, and they are gradually 

 carried down lower and lower, and at last 

 disappear. You know the Test, one of the 

 finest trout streams in Hampshire, and of 

 course in England: when I first knew this 

 stream, twenty years ago, there were no 

 grayling in it. A gentleman brought some 

 from the Avon, and introduced them into 

 the river at Longstock, above Stockbridge. 

 They were for two or three years very abun- 

 dant in that part of the river ; but they gra- 

 dually descended, and though they multiplied 

 greatly, there are now scarcely any above 



