136 THE LIFE OF THE SALMON 



are of great interest as showing that in each case 

 the lower river which flows from the large loch into 

 the sea has a markedly higher temperature than the 

 river above the loch. It is noticeable also, when the 

 charts which were prepared ^ are studied, that the 

 curves representing the mean weekly temperature 

 of the Ness and Awe (the lower rivers) are more 

 uniform in line or less quickly fluctuating than are 

 the curves for the upper waters. The Ness curve 

 during January, February, and March shows a 

 wonderfully flat inclination. The temperatures were 

 taken November 1901 till end of May 1902. I will 

 refer first to the Garry and Ness readings. From 

 the middle of December to the end of March the 

 weekly mean of the Garry never exceeds 40° F., and 

 in the middle of February, when the river was very 

 low after four weeks of continuous frost, the reading 

 reaches 35°. In April and May there is a steady 

 rise of temperature. The curve for the Ness runs, 

 however, at a distinctly higher level. In December, 

 January, February, and March there is constantly 

 from 2° to 8° difference in the readings. By the 

 middle of April the temperatures of the two rivers 

 have approximated by the rise in temperature found 

 in the Garry, the upper and early river. On referring 

 now to the curves representing the Orchy and Awe 

 temperatures, we notice first a much greater fluctua- 

 tion in both curves, but the same general result. 

 The Orchy is colder by 2° to 9° than the Awe, and 

 by the middle of April the curves appr6ximate by 



* Twenty-first Annual Report, Fishery Board for Scotland, II. 

 p. 76. 



