36 TKE ARCHITECTURE OF BIRDS. 
ter them from the weather, the indolence of that 
state in which the ingenuity of man has not been 
called forth by thought and experience, prevents 
them from constructing any additional convenience 
in the form of a door. Even when they take the 
trouble of making a wigwam of boughs, their sub- 
stitute for a door consists in narrowing the entrance 
so that it will only allow of their crawling in on all 
fours, like their fellow foresters, the bears and foxes. 
It is only after the dawn of refinement, when inven- 
tion has been stimulated by the desire of comfort, 
that we meet with doors curiously and tastefully 
constructed, possessing certain architectural pro- 
portions, as well as adapted to the character of the 
climate. Among the lower animals, the contri- 
vance of a door of any description is of rare occur- 
rence, and is, we believe, only to be found among a 
peculiar family of spiders (Mygalide). But all am- 
mals, man included, are soon taught by experience, 
that protection from enemies is no less necessary 
than shelter from the inclemencies of weather. The 
Gothic castle and the walled city have low and nar- 
row portals, opposed to the entrance of a hostile 
army; and the Indian contracts or barricades his 
hut to prevent his being devoured by nocturnal beasts 
of prey. 
It is probably both for protection from enemies 
and for shelter from the weather, that the nut-hatch 
(Sitta Europea) forms the barricade to her nest, 
which has suggested the preceding observations. 
In France, the bird is termed the mason woodpeck- 
er. The older naturalists tell us that this little ma- 
son selects for breeding the hole of a tree, and if 
this be larger than she requires, she narrows the en- 
trance with earth and mud so neatly kneaded that a 
potter could not do it more dexterously. Buffon 
adds, that she strengthens the fabric of soft earth 
with small stones, a device which we have observed 
