SIS Migration of Birds. 



quantity he was able to exhibit. It is true that since its dis- 

 covery selenium has been found in some ores of sulphur, 

 in the sulphureous mud of some manufactories of sulphuric 

 acid, and in some few kinds of concentrated sulphuric acid 

 itself, 3'et in such small quantities that the separation of it is 

 still very expensive. 1000 pounds of sulphuric acid containing 

 selenium will scarcely yield a drachm of that substance; and 

 in the largest manufactory scarcely four pounds, in a year, of 

 sulphureous mud will be deposited, yielding, after great labour 

 and expense, at the utmost only from 7 to 8 per cent, of se- 

 lenium ; and from the ores of sulphur themselves it is still 

 more difficult to be obtained. From these causes many che- 

 mists have not even seen this substance, much less have they 

 been able to make experiments with it. — Having been so for- 

 tunate as to pi'ocure a quantity from a source as yet unknown, 

 I offer to sell it to the friends of the science at the modei'ate 

 price of one Frederic's d'or the drachm, requesting that all 

 orders be sent post-paid, accompanied by the amount ; ob- 

 serving at the same time that the pi-esent stock [of material] 

 being consumed, I may perhaps not be able to procure a fresh 

 supply. — Dr. Joh. Bartli. Trommsdorf. 

 Erfurt, March 1, 1825, 



MIGRATION OF BIRDS. 



Dr. Schinz, secretary to the Provincial Society of Zurich, 

 has endeavoured to discover the laws according to which the 

 birds of Europe are distributed over our continent. The 

 country in which the bird produces its young is considered as 

 its proper one. The nearer we approach the poles, the more 

 do we find peculiar or stationary birds, and the fewer are the 

 foreign species which make their appearance. Greenland has 

 not a single bird of passage. Iceland has only one, which 

 remains during winter, and leaves it in spring for still more 

 northern countries. Sweden and Norway have already more 

 birds of passage ; and we find them increasing in number in 

 proportion as we advance towards the centre of Europe. In 

 the intertropical countries no bird emigrates ; to the north 

 they all emigrate. The propagation of birds keeps pace with 

 the quantity of food. Spitzbergen has but a single herbivorous 

 species ; for the sea presents more nutriment, and all the rocks 

 and cliffs are inhabited by aquatic birds. In the frigid zone, 

 a much greater number of marsh birds breed than beyond the 

 arctic circle and in the warm countries of Europe. Dr. 

 Schinz also indicates the distribution of the species of domestic 

 fowls ; and remarks, that each country has its peculiar varie- 

 ties of fowls.* — Bulletin Univcrs. {Edin. Phil. Joiirn.) 



* For Dr. Jeaner's investigation of the circumstances which impel birds 

 to migrate, sec Phil. Mag. vol. Ixiv. p. 50. STEAM- 



