18 OBSERVATIONS 



clear or discoloured, but a rather peculiar forma- 

 tion of the bed of the current seems to be required, 

 his favourite streams having now somewhat shal- 

 low and rapid, then long, slow-running, deep, 

 tracts ; in which latter places he poises himself 

 about three or four feet below the chain of insects, 

 &c. as at H H (see plate 1.) 



As he feeds principally on Larva? and flies, he 

 should, according to Malthus, be populous, (all 

 other things being equal), in proportion as these 

 insects are so. 



Temperature, both atmospheric and aqueous, no 

 doubt affects both the food and fish, as also may 

 the chemical properties of the stratum over which 

 the stream flows ; the mineral held in solution by 

 the fluid (which he breathes) cannot fail to affect 

 his constitution in some measure. 



But there exists no authority for the localities 

 of the Grayling at all comparable with Sir H. 

 Davy, who " has fished much in, and enquired 

 much respecting the places where it is found." 

 At p. 221 (Salmonia) he says, " In the Test, where 

 the Grayling has been only recently introduced, 

 they have sometimes been caught between three 

 and four pounds ; in this river I never took one 

 above two pounds, but I have heard of one being 

 taken of two pounds and a half. The Grayling 

 is a rare fish in England, and has never been found 

 in Scotland or Ireland ; and there are few rivers 



