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 isepipteses (icos, = xqualis, erixtnow = 
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 progress made by 
the species in different longitudes, and assuming that the advance 
is directly across the isepiptesial lines, or rather the belts defined 
by each pair of them, the whole 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 Siberia 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. Palmén, of whose work,® originally published in 
1 Die Isepiptesen Russlands. Grundlagen zur Exrforschung der Zugzeiten wnd 
Zugrichtungen der Vogel Russlands. St. Petersburg: 1855. 
2 Hirundo rustica, Motacilla alba, Alauda arvensis, Oriolus galbula, Cuculus 
canorus, Ciconia alba and Grus communis. 
3 Om Foglarnes fiyttningsvagar (Helsingfors: 1874). In this and the work 
of Dr. von Middendorff, already cited, reference is made to almost every im- 
portant publication on 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 Ornithologiz (i. pp. 146-155). - Yet mention may be 
made of Schlegel’s Over het trekken der Vogels (Harlem: 1828), Mr. Hodgson’s ‘‘ On 
the Migration of the Natatores and Grallatores as observed at Kathmandu” in 
