178 THE NATURAL HISTORY 



of moist earth." Hence we see that water, by its coolness, 

 is enabled to assimilate to itself a large quantity of moisture 

 nightly by condensation ; and that the air, when loaded 

 with fogs and vapours, and even with copious dews, can 

 alone advance a considerable and never-failing resource. 

 Persons that are much abroad, and travel early and late ; 

 such as shepherds, fishermen, etc. can tell what prodigious 

 fogs prevail in the night on elevated downs, even in the 

 hottest parts of summer ; and how much the surfaces of 

 things are drenched by those swimming vapours, though, 

 to the senses, all the whUe, litde moisture seems to faU. 



I am, etc. 



LETTER XXX 



TO THE HONOURABLE DAINES BARRINGTON 



Selborne, April 3, 1776. 



Dear Sir, 

 Monsieur Herissant, a French anatomist, seems per- 

 suaded that he has discovered the reason why cuckoos do 

 not hatch their own eggs ; the impediment, he supposes, 

 arises from the internal structure of their parts, which 

 incapacitates them for incubation. According to this 

 gentleman, the crop or craw of a cuckoo does not lie 

 before the sternum at the bottom of the neck, as in the 

 gallinae, columbae, etc. but immediately behind it, on and 

 over the bowels, so as to make a large protuberance in the 

 beUy.i 



Induced by this assertion, we procured a cuckoo ; and, 

 cutting open the breast-bone, and exposing the intestines 

 to sight, found the crop lying as mentioned above. This 

 stomach was large and round, and stuffed hard like a pin- 

 cushion with food, which, upon nice examination, we found 

 to consist of various insects ; such as small scarabs, 

 spiders, and dragon-flies ; the last of which we have seen 



^ Histoire de I'Acaddmie Royale, 1752. 



