106 BIRD LIFE ON ISLAND AND SHORE 
through, scores of revolving rings of Grey Petrel— 
Mutton bird,—some of the circles consisting of 
hundreds and some of thousands, but each appa- 
rently self-contained and not mingling with other 
groups. About the centre of each ring thronged © 
birds in every attitude of motion and repose, some 
momentarily quiescent, gorged, others feeding in 
furious haste, till in their turn ousted by new- 
comers fiercely impatient for their share in the 
feast. There were birds on the water, birds about 
to alight on it, birds rising from it, all pursuing 
the same circular course, until each moving mass 
became a waterspout of birds, narrow at the base, 
wider above, its particles rapidly gyrating in the 
one direction. The hollow circle shape, or rather 
vase shape, for it narrowed at bottom, was due 
presumably to the constricted area on which the 
food was floating and to the wheeling drop to 
water of bird after bird in unending succession. 
There was no room for divergence of flight ; each 
individual had perforce to follow his neighbour 
in a circular fall to ocean, and again to follow 
his neighbour in a circular upward rise. Birds 
ousted from the water by the crush seemed, after 
a moment’s sidewise pause, to gather sufficient 
impetus to begin the round once more. From the 
food-supply centre they spun in wide and wider 
circles, far flung as if by some centrifugal force, 
each individual gyrating with desperate velocity ; 
