Indeed, it was certain that one member of the flock was a rarity, if not an absolute novelty. That was the most exciting and by all odds the most deplorable incident of the whole affair. I had obtained several glimpses of him, but had been unable to determine his identity; a warbler, past all reasonable doubt, with pure white under parts (the upper parts quite invisible) except for a black or blackish line, barely made out, across the lower throat or the upper breast. He, of course, had vanished with the rest, the more was the pity. I had made a guess at him, to be sure; it is a poor naturalist who cannot do as much as that (but a really good naturalist would “form a hypothesis,” I suppose) under almost any circumstances. I had called him a cerulean warbler. Once in my life I had seen a bird of that species, but only for a minute. If he wore a black breast-band, I did not see it, or else had forgotten it. If I could only have had a look at this fellow’s back and wings! As it was, I was not likely ever to _know_ him, though the printed description would either demolish or add a degree of plausibility to my offhand conjecture. The better course, after losing a bevy of wanderers in this way, is perhaps to remain where one is and await the arrival of another detachment of the migratory host. This advice, or something like it, I seem to remember having read, at all events; but I have never schooled myself to such a pitch of quietism. For a time, indeed, I could not believe that the birds _were_ lost, and must hunt the hilltop over in the hope of another chance at them. An empty hope. So I did what I always do: the game having flown, I took my own departure also. I should not find the same flock again, but with good luck--which now it was easy to expect--I might find another; and except for the single mysterious stranger, that would be better still. One thing I was sure of,--Natural Bridge was not to be left out of the warbler migration; and one thing I forgot entirely,--that I had planned to leave it by the noonday train.