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make good difpatch, and conld remark how much 
they had fcooped that day, by the frefli fand which ran 
down the bank, and was of a different colour from that 
which lay loofe and bleached in the Sun. In what 
fpace of time thefe little artifts are able to mine and finifli 
thefe cavities I have never been able to difeover, for rea- 
fons given above ; but it would be a matter worthy of 
obfervation, where it falls in the way of any naturalift 
to make his remarks. This I have often taken notice of, 
that feveral holes, of different depths, arc left unfiniflied 
at the end of fummer. To imagine that thefe begin- 
nings were intentionally made in order to be in greater 
forwardnefs for next fpring, is allowing, perhaps, too 
much forefight and rerum prude?itia to a fimple bird. 
May not the caufe of thefe latehm being left unfiniflied 
arife from their meeting in thofe places with Jirata too 
hard, harfli, and folid for their purpofe, which they re- 
linquifli, and go to a frefli fpot that works more freely ? 
Or may they not in other places fall in with a foil as 
much too loofe and mouldering, liable to flounder, and 
threatening to overwhelm them and their labours ? 
One thing is remarkable, that after fome years the old 
holes are forfaken, and new ones bored; perhaps becaufe 
the old habitations grow foul and fetid from long ufe; 
or becaufe they may fo abound with fleas as to become 
untenantable. This fpeeies of fwallow, moreover, is 
ftrangely annoyed with fleas; and we have feen fleas, 
bed-fleas (pulex irritans) fwarming at the mouths of 
thefe holes like bees on the ftools of their hives. When 
they 
