164 
THE NATURAL HISTORY 
[LETT, 
and so nearly correspondent in their general mode of life ! ^ For 
while the s\^ allow and the house-martin discover the greatest 
address in raising and securely fixing crusts or shells of loam as 
cunahula for their young, the bank-martin terebrates a round and 
regular hole in the sand or earth, which is serpentine, horizontal, 
and about two feet deep. At the inner end of this burrow 
does this bird deposit, in a good degree of safety, her rude nest, 
consisting of fine grasses and feathers, usually goose-feathers, 
very inartificially laid together. 
Perseverance will accomplish anything : though at first one 
would be disinclined to believe that this weak bird, with her 
soft and tender bill and claws, should ever be able to bore the 
stubborn sand-bank wdtliout entirely disabling herself; yet with 
these feeble instruments have T seen a pair of them make great 
despatch : and could remark how much they had scooped that 
day by the fresh sand which ran down the bank, and w^as of a 
different colour from that which lay loose and bleached in the 
sun. 
In what space of time these little artists are able to mine and 
finish these cavities I have never been able to discover, for rea- 
sons given above ; but it would be a matter worthy of observa- 
tion, where it falls in the way of any naturalist to make his 
remarks. This I have often taken notice of, that several holes 
of different depths are left unfinished at the end of summer. 
To imagine that these beginnings were intentionally made in 
order to be in the greater forwardness for next spring is allowing 
perhaps too much foresight Q.B.d rerum j^rudentia to a simple bird. 
May not the cause of these latebrce being left unfinished arise from 
their meeting in those places with strata too harsh, hard, and solid 
for their purpose, which they relinquish, and go to a fresh spot 
that works more freely ? Or may they not in other places fall 
in with a soil as much too loose and mouldering, liable to foun- 
der, and threatening to overwhelm them and their labours ? 
^ " Each creature hath a wisdom of its owji ; 
The pigeons feed their tender offspring, crying, 
When they are callow, but withdraw their food 
AVhen they are fledged, that they jnay teach them flying." 
Herbert, 
