98 REPORT ON THE MIGRATION OF BIRDS. 



witnessed, such data would assuredly lead to most interesting, 

 useful, and scientific results. 



One great difference in the migration of Gulls in 1884-5 from 

 that of 1872-3 is that in 1884-5 there were very few Glaucous 

 Gulls (Larus glaucus) or Iceland Gulls (L. ishuidicus), hut in 

 1872-3 hoth these species were in vast numbers, comparatively 

 speaking. It seems to me possible that the 1872-3 migration 

 indicated by these Arctic Gulls was of even wider and more 

 extensive influence than that of 1884-5. But of course there is 

 room here for still further elucidation and collection of statistics. 



Again, while the Tay usually is visited by sprats in great 

 sprat seasons, equally, or nearly so, with the Forth, and was so 

 visited in 1872-3 though not to the extent that the Forth was, 

 in 1884-5 it appears to have been almost utterly deserted by 

 fish and bird alike. The cause was, no doubt, comparative 

 scarcity of entomostracan life, dependent, most likely, upon 

 certain undefined conditions of sea-temperatures, affected, pos- 

 sibly, from the river-basin of Tay and its tributaries. If light 

 can be thrown upon these not-difficult-to-ascertain data, in a 

 few years, at most, much of our uncertainty as to causes and 

 effects of migration of Entomostraca, Sea-fish, and even Salmon 

 and migratory Salmonidse will be removed. 



Temperatures of the Firth of Forth, June, 1884 to January, 1885. 



Isle of May. Queensferry. Near Alloa. 



June (1884) 



July 



August 



September 



October 



November 



December 



January (1885) 

 Range of surface tempera- 

 ture of the water 

 Xote. — The figures in brackets were not observed, but are 

 entered hypothetical!} 7 . 



Mr. Milne, in writing to me, adds* " I believe that in hot 

 summer days the temperature at Alloa would be 70° or more, 

 and during severe winter weather would certainly be down 



51 



53 



58 



(52) 



58 



(60) 



54 



(59) 



(M) 



(53) 



54 



58 



53 



52 



51 



49 



47 . 



45 



44 



41 



(38) 



(43) 



39 



35 



- 10° ^ 



20° 



30° 



