ELECTEIC INFLUENCE. 119 



with non-conducting materials. The run of the 

 nest always turns inwards, so as to apply itself 

 closely to the body of the parent while sitting 

 on her eggs ; and we have seen that she per- 

 forms her task most assiduously during heavy 

 rains, which, in the intertropics, are connected 

 with electric changes in the atmosphere. At 

 the same time, as the Humming-birds generally 

 breed at an early season of the year, when the 

 air is less saturated with electricity than it is at 

 a later period, there is the less necessity for the 

 additional security of a dome. Every nest will, 

 of course, husband the animal heat given out 

 from the body of the parent during incubation, 

 but this applies generally; and we have no 

 reason to suppose that the body of the Hum- 

 ming-bird imparts so little heat to her two eggs, 

 as to render the thickness and depth of the nest 

 on that account more especially necessary : and 

 we think that the reason may be better explained 

 on the theory proposed by Mr. Hill, a theory 

 applicable more or less directly to all the soft, 

 mossy, or downy nests of arboreal birds, which 

 thus subserve two purposes, they husband the 

 nest generated by the parent during incubation, 

 and act as non-conductors of electricity when 

 thunder-storms disturb the atmosphere. In 

 domed nests the isolation of the eggs is the most 

 complete. 



Considering that the Humming-birds never 

 lay more than two eggs, the abundance of cer- 



