410 INSECTIVOILE. 



The nest is altogether one of the most extraordinary of 

 animal structures. It is built wholly of gathered r/i ate rials, 

 without any secretion by the birds either as a cement or 

 otherwise. That any bird uses a secretion of its own body 

 in the construction of its nest, cannot indeed be regarded as 

 an absolutely demonstrated truth, and in the case of the 

 long-tailed tit, rational hypothesis does not go so far even as 

 to lead to the belief that any of the materials adhere to 

 each other by being glutinous, because in that case they 

 would be as likely to adhere to the dry surface of the bill, 

 or at least to the produced feathers at its base, as to anything 

 else. Thus, the nest in question must be regarded as being 

 wholly a mechanical structure, owing its compactness to the 

 manner in which the materials are put together ; and, in the 

 mere union of its parts, perhaps it is the finest mechanical 

 structure, independently of living structures, that is any 

 where to be met with. The best of human workmen would 

 find more difficulty in imitating the execution of a long-tailed 

 tit's nest, than in imitating any work of human art. 



Nor is that at all to be wondered at, when we consider the 

 implements with which it is made. The power which the 

 bird has of perching on one foot, if necessary, so as to have 

 perfect command of its whole body ; the nice, yet powerful 

 forceps formed by the firm, short, and pointed bill ; the in- 

 numerable motions that may be given to them by their own 

 peculiar muscles, and the motions of the neck, and of the 

 whole body, if necessary ; and the high magnifying power of 

 the eye, which guides the whole ; are altogether vastly supe- 

 rior to any set of tools with which man can be furnished. A 

 power of four, or one inch and a quarter focal length, is 

 inconvenient even in very small works, and a power of six 

 has so small a field, that it can hardly be used ; but the 

 bird has a power of more than twelve in its natural sight 

 so that, with that power, it commands any extent of field, 



