TIME OF THE MIGRATION OP BIRDS, SS 



be taken as the basis of calculation, which is the maximum 

 that I have obtained, the amalgam would contain about 

 y-^y^-f, of new matter, on the antiphlogistic view, and about 

 ^^7 on the phlogistic view. 



I shall have occasion to recur to, and to discuss more New modes of 

 fully these ideas, and I shall conclude this section by l^^^'itrolT" 

 stating, that, though the researches on the decomposition ^5'^' and voia^ 

 and composition of nitrogen, which have occupied so large ggsted, ^ ^ 

 a space in the foregoing pages, have been negative, as to the 

 primary object, yet they may not possibly be devoid of 

 useful applications. It does not seem improbable, that the 

 passage of steam over hot manganese may he applied to 

 the manufacture of nitrous acid. And there is reason to 

 believe, that the ignition of charcoal and potash, and their 

 exposure to water, may be advantageously applied to 

 the production of volatile alkali, in countries where fuel i% 

 cheap. 



^To be concluded in our next. J 



VI. 



Times of Migration of some of the Swallow Tribe, Sfc.y near 

 London, In a Letter from Thomas Forster, Esq, 



To Mr. NICHOLSON. 

 SIR, 



►SHOULD you consider the following table, showing the 

 periods of the earliest and latest appearance of several of 

 the swallow tribe, &c.,at Clapton, during some years, worth 

 insertion in your Journal, it is much at your service. It 

 may amuse some of your numerous readers, and will 

 oblige your constant reader, 



THOMAS FORSTER. 



EARLIEST 



