146 Zoological Society, 



" Naturalists have remarked," observes Mr. Hill, " that in tropical 

 countries there are a greater number of birds that build close nests 

 than in the temperate climate of Europe. In the West Indian islands, 

 with the exception of the Pigeon tribes and the Humming-birds, the 

 nests are almost uniformly circular coverings of dried grass, varied 

 by intermingled cotton, moss, and feathers, with an opening from 

 below, or an entrance at the side. The Banana-bird weaves a 

 hammock of fibres, sometimes of horse-hair, deep and purse-like, and 

 loosely netted ; the Muscicapa olivacea a hanging cot of withered 

 leaves, straw, moss, fibrous threads, and spiders' webs, fitted together, 

 and the Mocking-bird builds in the midst of a mass of wicker-work 

 a neat nest of straw, lined with hair. The Woodpecker and the 

 Parrots take to hollow trees, but I hardly know an arboreal bird be- 

 side that constructs any nest that is not wholly covered or domed 

 over. Very many insects that are exposed to the air during their 

 metamorphoses weave coverings of silk and cotton, in which they lie 

 shrouded, at once impenetrable to moisture, and uninfluenced by the 

 disturbances of the atmosphere. It would seem that the object, 

 whatever it be, is the same in both. It is not for warmth that the 

 insects spin these webs, for they form their coverings of silk and 

 cotton in the hottest period of the year ; and I find, that whilst all 

 our birds that build open nests breed early, those that construct 

 the domed and spherical ones, nestle in the season between the spring 

 and autumnal rains, when the air is saturated with electricity, and is 

 in a state of constant change. 



" The destructive influence exercised by the active electricity of 

 the atmosphere on the eggs of birds, accords with that organic gra- 

 dation by which the higher embryonic animals commence vegetative 

 life with an organization similar to that of the lower. The success- 

 ive stages of development presented by the egg during incubation 

 exhibit the heart and great vessels constructed like those of the Ba- 

 trachian reptile, with reference to a bronchial circulation. In the 

 descending scale of organization, in animals, where the respiration 

 is low and the irritability high, the electric stimulus is rapidly fatal. 

 Fish and Crustacea perish in numbers under the influence of a thun- 

 der-storm (Art. Irritability, Cyclop. Anat. and Phys.), and the half- 

 matured embryo in the egg is destroyed by the disturbances which 

 prevail during the activity of the summer lightning. 



" Electricity being entirely confined to the surface of bodies, and 

 the quantities they are capable of receiving not following the pro- 

 portion of their bulk, but depending principally upon the extent of 

 surface over which it is spread, the exterior of bodies may be posi- 

 tively or negatively electric, while the interior is in a state of perfect 

 neutrality. Under isolation the quiescent state of the electricity 

 occasions no sensible change in their properties. The power of re- 

 taining the electric fluid depending upon the shape, and the sphere 

 and the sjjheroid retaining it readily, while it escapes from a point, 

 or is received by a point with facility, the enveloping the eggs of 

 birds in dried and non-conducting materials spread entirely and 

 widely round is a means of steadily maintaining a uniform distri- 

 bution of the electricity, and with it of preserving that state of qui- 



