the air; when they frequently uſe their feet alſo, which, being webbed, ſerve them to make ſeveral ſtrokes againſt the water, in order to raiſe themſelves out of it. This impulſion being once given, they have no more occaſion to ſtrike their wings together, but hold them very widely expanded, whilſt they ſail along, balancing their bodies alternately from right to left, and ſkimming ſwiftly over the ſurface of the ſea in queſt of their food. This mode of poiſing themſelves in the air undoubtedly ſerves to accelerate their flight, but one can hardly ſuppoſe it to be ſufficient for ſupporting them above the ſurface. Perhaps ſome imperceptible tremulous motion of their feathers may be the principal cauſe of their extraordinary mode of flying. If that be the caſe, they muſt be provided with ſome particular muſcles adapted for the purpoſe; on which account I think that the ſtructure of the albatroſs deſerves to be very attentively inveſtigated by anatomiſts.
The puffins of Buffon (procellaria puffinus), were very numerous in theſe ſeas. The flight of this bird is performed in a manner analogous to that of the albatroſs, for he often ſkims along for a great length of time without any perceptible motion of his wings: it is only when he changes his oblique poſition from one ſide to the other
that
