OF SELBORNE 203 



from experiment, that " the moister the earth is the more 

 dew falls on it in a night : and more than a double 

 quantity of dew falls on a surface of water than there 

 does on an equal surface 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 con- 

 siderable 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, little moisture seems to fall. 



I am, etc. 



LETTER XXX 



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 gallinxj columbse, etc., but immediately behind it, on 

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

 in the belly.* 



* Histoire de I'AcadSmie Rogale, 1752. 



