“180 THE NATURAL HISTORY OF SELBORNE, 
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 vapors, 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 vapors, though, to the 
senses, all the while, little moisture seems to fall. 
LETTER XXX. 
SELBORNE, April 3rd, 1776. 
Monsieur Hérissant, a French anatomist, seems persuaded 
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 poultry, pigeons, etc., but immediately behind 
it, on and over the bowels. 
Induced by this assertion, we procured a cuckoo; and, 
cutting open the breastbone, 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 cuckoos catching on the 
wing as they were just emerging out of the aurelia state. 
Among this farrago also were to be seen maggots, and many 
seeds, which belonged either to gooseberries, currants, cran- 
