252 FRIENDS WORTH KNOWING. 
further remarked that some of these martins’ holes are 
nearly as circular as if they had been planned out with a 
pair of compasses, while others are more irregular in form ; 
but this seems to depend more on the sand crumbling away 
than upon any deficiency in its original workmanship. The 
bird, in fact, always uses its own body to determine the 
proportions of the gallery, the part from the thigh to the 
head forming the radius of the circle. It does not trace 
this out as we should do, by fixing a point for the centre 
around which to draw the cireumference; on the contrary, 
it perches on the circumference with its claws, and works 
with its bill from the centre outward;..... the bird conse- 
quently assumes all positions while at work in the interior, 
hanging from the roof of the gallery with its back down- 
ward as often as standing on the floor. We have more 
than once, indeed, seen a bank-martin wheeling slowly 
round in this manner on the face of a sand-bank when it 
was just breaking ground to begin its gallery. , 
“This manner of working, however, from the circumfer- 
ence to the centre unavoidably leads to irregularities in the 
direction...... Accordingly, all the galleries are found to 
be more or less tortuous to their termination, which is at 
the depth of from two to three feet, where a bed of loose 
hay and a few of the smaller breast-feathers of geese, ducks, 
4 
