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 while, litde moisture seems to fall. 



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 He 

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

 gallinae, columhae^ etc. but immediately behind It, on and 

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

 belly.^ 



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 1' Academic Royale, 1752. 



