MIGRATION 559 



collated the records of the arrival of migratory Birds throughout 

 the Russian Empire, but the insight into the question afforded by 

 his published labours ^ is not very great. His chief object was to 

 trace what he termed the isepi])teses {1xto% — xqualis, eiriTrr'ijcns = 

 advolatus) or the lines of simultaneous arrival, and in the case of 7 

 species ^ these are laid down on the maps which accompany his 

 treatise. The lines are found by taking the average date of arrival 

 of each species at each place in the Russian dominions where 

 observations have been regularly made, and connecting those places 

 where the dates are the same for each species by lines on the map. 

 The curves thus drawn indicate the inequality of progi'ess made by 

 the species in diff"erent longitudes, and assuming that the advance 

 is directly across the isepiptesial lines, or rather the belts defined 

 by each pair of them, the Avhole course of the Migration is thus 

 most accurately made known. In the case of his seven sample 

 species the maps shew their progressive advance at intervals of a 

 few days, and the issue of the whole investigation, according to 

 him (op. cit. p. 8) proves that in the middle of Sibei"ia the general 

 direction of the usual migrants is almost due north, in the east of 

 Siberia from south-east to north-west, and in European Russia from 

 south-west to north-east. Thus nearly all the migrants of the 

 Russian Empire tend to converge upon the most northern part of 

 the continent, the Taimyr Peninsula, but it is almost needless to say 

 that few of them reach anything like so far, since the country in 

 those high latitudes is utterly unfit to support the majority. With 

 the exception of some details, which though possessing a certain 

 special interest, need not here be mentioned, this treatise fails to 

 shew more ; for the fact that there are places that notwithstand- 

 ing their higher latitude are reached by Birds on their spring 

 migrations sooner than others in a lower latitude was already 

 known, and indeed may be to some small extent observed even in 

 England. 



The routes followed by migratory Birds have been the subject 

 of enquiry by many naturalists, among whom must be especially 

 named Prof. Palm^n, of whose work,^ originally published in 



^ Die Isepiptesen Russlands. Grundlagen zur Erforscliung der Zugzeiten und 

 Zagrichtungen der Vogel Russlands. St. Petersburg : 1855. 



^ Hirundo rustica, Motacilla alba, Alauda arvensis, Oriolus galbula, Cuculus 

 canorus, Ciconia alba and Grus coTnmunis. 



^ Om Foglarnes flyttningsvdgar (Helsingtbrs : 1874:). In this and the work 

 of Dr. von Middendorft", already cited, reference is made to almost every im- 

 portant publication ou the subject of Migration, which renders a notice of its 

 very extensive literature needless here, and a pretty full bibliographical list is 

 given in Giebel's Thesaurus Ornitliologise (i. pp. 146-155). Yet mention may be 

 made of Schlegel's Overhet trekken der Vogels (Harlem : 1828), Mr. Hodgson's "On 

 the Migration of the Natatorcs and Grallatores as observed at Kathmandu " in 



