OF SELBOBNE, 
199 
tlie bank, and was of a different colour from that wliicli 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 reasons given above ; but it would be a matter worthy 
of observation, 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 for- 
wardness for next spring, is allowing perhaps too much fore- 
sight and rerum prudentia to a simple bird. May not the 
pause of these latebrcB being left unfinished arise from their 
SAND martin's NEST. 
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 mould- 
ering, liable to founder, and threatening to overwhelm them 
and their labours ? 
One thing is remarkable — that, after some years, the old 
holes are forsaken and new ones bored ; perhaps because 
the old habitations grow foul and fetid from long use, or 
because they may so abound with fleas as to become unten- 
antable. This species of swallow moreover is strangely 
annoyed with fleas : and we have seen fleas, bed fleas (Pulete 
