APPENDIX. 233 



but I once heard of an experiment being tried in the 

 following manner : Equal numbers of trout were confined 

 for a certain time by gratings to three several portions 

 of the same stream. The fish in one of the divisions were 

 fed entirely upon flies ; in another, upon minnows ; and in 

 the third, upon worms. At the end of a certain period, 

 those which had been fed on flies were the heaviest and in 

 the best condition ; those fed on minnows occupied the 

 second place ; while those fed on worms were in much the 

 worst order of the three. The probability is, that had 

 another pen been set off, and the fish fed with a mixture 

 of all three species of food, the fish in it would have far 

 exceeded any of the others in weight and condition. 



" Some rivers notoriously produce larger trout than 

 others, although the character of the soil they flow through 

 may to all appearance be very similar. I will instance two, 

 both of which are tributaries of the Thames the Chess, a 

 branch of the Buckinghamshire Colne ; and the Wick, a 

 little stream running through High Wycombe. I select 

 these two streams, because they are only some ten or twelve 

 miles from each other, and because they are as nearly as 

 possible of a size. Now, it is generally supposed that the 

 very best and most fattening food provided by Nature for 

 the trout is the may-fly, or green-drake. This fly abounds 

 in profusion on the Chess ; it is rarely if ever seen on the 

 Wick in fact, it may be said not to exist there. The min- 

 now, likewise supposed to be most excellent and nourishing 

 food for the trout, is also a stranger to the Wick ; or if it 

 exists there, is not found in any considerable number. 

 Sticklebacks and miller's thumbs are found in places, 

 though they do not abound in all parts of the stream. The 

 caddis, or case grub of the smaller flies, however, is very 

 abundant; and in some of the hatch-holes there are a 

 considerable quantity of leeches. 

 20* 



