1865.] Dr. Davy on the Temperature, fyc., of Birds. 451 



the quill tail-feathers, is well known to the naturalist. In all the instances 

 in which I have weighed the primates of each wing, I have found them, if 

 not precisely of the same weight, to diifer in the smaller birds not more 

 than by p l or '01 grain, and in the larger the difference has rarely exceeded 

 1 grain ; a degree of equality this which might be expected, as essential 

 to the regularity of flight ; and small as it is, I am disposed to think that 

 in the larger birds even it would hardly be appreciable could the quills be 

 extracted with precisely the same proportion of adhering tissue. 



Comparing the quill-feathers of the small with those of the large birds, 

 the proportional weight of the latter, it would appear, is commonly greater 

 than that of the former, a disproportion, it may be inferred, connected 

 with the larger birds having, as needed, stronger wing- and tail-quill fea- 

 thers, and, indeed, stronger feathers generally, the few exceptions harmo- 

 nizing, at least those of the common fowl and duck. 



Comparing their bones, those of the larger and more powerful, as might 

 also be anticipated, appear, too, proportionally heaviest. 



Comparing individuals of the same species, whether as to the total weight 

 of birds, or of feathers and bones, variations will be found to occur. The 

 skylarks may be mentioned as examples, and also the tits, the former ob- 

 tained not from the same locality, one having been procured from Lincoln- 

 shire, one from Oxfoid, a third from Yorkshire, a fourth from the imme- 

 diate neighbourhood of Ambleside, where it is rarely seen, and where it 

 came during a severe frost probably in quest of food, having been found 

 close to a running stream* ; the tits were all from the immediate neigh- 

 bourhood of Ambleside. 



3rd. Of the weight of the principal bones of the skeleton, The results 

 obtained are given in the next Table. The birds, the bones of which 

 were the subjects of trial, have already been all mentioned, and may be 

 identified by their weight, as inserted again in the first column. With 

 the cranium, it may be stated, the maxillae and facial bones were weighed, 

 and with the pelvis the caudal vertebrae : the spine comprised all the other 

 vertebrae excepting those anchylosed with the pelvis ; the terminal bones 

 of the extremities are designated by metacarpi, &c. for the upper, and by 

 phalanges for the lower. 



* In the gizzard of all the larks I have examined I have found grass, tending to prove 

 that, at least in winter, meadow-grass is their chief food. 



