Memoirs of the Lit. and Phil. Society of' Manchester. 159 



Mr. Blackwall proceeds to inquire if there is any connexion between 

 the mean temperature of the times of the appearance and disappearance 

 of periodical birds ; but it is quite obvious from his tables, and from 

 similar tables in other latitudes, that the weather is, generally speaking, 

 much colder when they appear than when they disappear, from which 

 we should be disposed to draw the conclusion, that they have a greater 

 affection for our temperate one than for the warm climate to which they 

 emigrate in winter. 



In order to show that the periodical birds migrate to warmer climates, 

 in place of becoming torpid in winter, as has been supposed by some na- 

 turalists, Mr. Blackwall derives his principal arguments from the ab- 

 surdity of the latter opinion. He also argues from the important fact, 

 that several species of periodical summer birds moult during the interval 

 that elapses between their departure and re-appearance ; and he consid- 

 ers it ridiculous to suppose that these birds could throw off their old fea- 

 thers and put on new ones, if they were in a state of torpidity, or if their 

 animal functions were entirely suspended. 



Mr. Blackwall has enriched this volume with other two papers, one 

 On the Notes of Birds, including an Enquiry whether or not they are in- 

 stinctive, and another On the Cuckoo. 



In the first of these papers, he clearly shows, in opposition to Daines 

 Barrington, that the notes of birds are instinctive, and do not " depend 

 on the master under whom they are bred." His principal observations 

 are arranged in tables, which we cannot withhold from our readers, 

 and which we have thrown into one. 

 Table V. — Catalogue of Singing Birds, with the time of their beginning 



and ceasing to sing, from a mean of five years' observation, with the 



numerical value of their notes, twenty being that of absolute perfection. 



