^ Lucky Friday, 75 



he was at liberty ; a comfortable, stout, happy little man 

 all in black. Discourse touching Birds and Bird-hunters, 

 ... at last, the theory (of Migration of Birds) as based upon 

 the Isothermals. Granted in part, encouraged in part, 

 but with many, many difficulties. Surveys not sufficient ; 

 endless labour ; strong cases against it; but a fine project, 

 though wild. With the greatest kindness and affability 

 Mr. Y. offered the free and unrestricted use of his most 

 perfect library for my purpose. How few would have been 

 so generous, and on a first visit ! ... In some instances 

 he told me there is a strange movement from the ' pole ' 

 when species from both Continents are scattered as it were 

 abnormally, either caught up in a whirl of circular storm, 

 or altogether thrown out of their reckoning. Thus occur 

 at about the same time the White-winged Crossbill of 

 America and that of Europe on our ground. (The Esqui- 

 maux Curlew, if rightly named, may be another instance. 

 A. G. M.) The fact being that the migratory impulse 

 becomes so strong upon them that move they must, and by 

 some error in calculation lose themselves, alighting then 

 on the first met (and southern) land. 



" I however should give more to temperature and to bird 

 instinct to avail itself of that. Feeling their way from the 

 rigorous and dry (soon to be snow-swept) plain of the 

 central Continent, they pass along to a more genial clime, 

 skirting the great mountain ridges, following shores, 

 valleys (river-courses r) towards the maritime climate of 

 the softening ocean-influence. And the Gulf Stream, we 

 know its influence as a great thermal. Why do we map 

 its course, and yet bind down the movements of Birds so 

 strictly North and South, denying them consequently the 

 free exercise of those instincts which were intended for 

 their well-being r It is to prefer the straight degrees of 

 latitude to the Isothermal curves."* 



* The Theory of Bird Migration, here referred to, is one which he never elabo- 

 rated in print, though for many years he lost no opportunity of collecting facts 

 seeming to bear upon it. The "Remarks on the Migration of Birds," which he 

 contributed to the " Zoologist " in 1859, drew attention to some of the hitherto 

 little-observed facts on which his theory was based ; and he certainly appears to 

 have been one of the earliest naturalists to have been struck with the westerly 

 course followed by so many autumnal migrants across Europe and Asia. 



