big-horn, how is it possible they could have seen it?"

"I do not say they have; but they have seen others, who have seen
others, who in their turn have seen others, who actually _have_ seen the
carrion."

"Oh! I understand; you mean that some one or more have first spied it;
and, while making towards it, have been observed by others at a greater
distance; and those again who have followed them have been followed by
others still more distant, and so on."

"Precisely so; and this at once accounts for the fabulous stories of
vultures scenting carrion at the distance of miles--none of which
stories are true, but have been propagated by men who, perhaps, never
saw a vulture in the air, but who, in order to make their books amusing,
have readily adopted the exaggerated tales of every Munchausen they
could meet with."

"Your theory is certainly the more probable one."

"It is the true one. It has been proved to be so by numerous
experiments with vultures; all of which have gone to show, that these
birds have anything but a keen sense of smell. On the contrary, it is
remarkably weak; and I think it is well for them it is so, considering
the sort of food they live upon."

"This flock must have gathered from all parts," remarked Francois; "we
see them coming in from every point of the compass. No doubt some of
them have travelled fifty miles."

"As likely an hundred," rejoined Lucien. "Such a journey is a mere
bagatelle to them. Now, if I knew the precise moment at which the
carrion was discovered by the first one, I could tell how far each of
the others had come--that is, each of them whose arrival we are now
witnessing."

"But how could you do that, brother?" demanded Basil and Francois, in
astonishment; "pray tell us how?"

"I should make my calculation thus:--In the first place, they have all
started _at the same time_."

"At the same time!" interrupted Basil; "how can that be, if some of them
were an hundred miles off?"

"No matter what distance," replied Lucien; "it is all the same. They
have all commenced their flight hither, not _exactly_, but _nearly_, at
the same moment. Is it not plain? These birds, while hunting for their
food, sweep through the air in great circles. Each of these circles
overlooks a large tract of the earth's surface below. Their
circumferences approach or intersect each other--so that, in fact, the
whole country is under a network of them. Now, as soon as one of the
vultu