FOOD-SUPPLIES AND RELEVANT MATTERS 107 



the amount of Crustacea garnmari, etc. and 

 I remember the trout in the chalk streams 

 of Wiltshire were often in good condition 

 by the end of March. Streams flowing 

 through " drift-covered " country like the Don 

 are again likely to be earlier than those in 

 which there is much bare rock and shifting 

 shingle channel; but I do not think that, 

 with the exception of limestone and chalk, 

 the nature of the rock makes much differ- 

 ence. Elevation, temperatures, and snow- 

 water are probably the chief factors.' Illus- 

 trative of this, and speaking of the very cold, 

 bleak May of 1898, he adds : ' This has been 

 a very cold, bleak season, and such few trout 

 as there are here (he is writing from a locality 

 high up in Lochaber), have been very late 

 of getting into condition, while there has 

 been hardly any fly to speak of, though 



red-spinners were out on the Burn in 



pretty large numbers on the 23rd May. I 

 suspect you have not done so well on the 

 Deveron as usual/ (See our ' Comparison and 

 History of Seasons/ ante, p. 105.) 



That seasonal changes take place in fish at 

 different times and even among different in- 



