"Yes, Frank, you have caught me; these travellers are martins; and, if you wish, I will tell you more about them. Mr. Wilson, whom I have been reading to-day, calls them birds of passage."
"What does that mean, Mother?"
"It means that they find it necessary for their support to pass from one country to another when winter is coming on. At that time they leave us.
"Some people think that martins and swallows hide themselves from the cold in holes in rocks and banks, or in hollow trees; but Wilson, who spent many years in watching the habits of birds, and learning their history, thinks that these fly a great way off to a warmer country as winter approaches, and that they return again in the spring."
"But how can they find the way?" asked Frank.
"All that we know about that, Frank, is, that He who created the martins has given to them the knowledge that guides them right. In their long way through the pathless air, they never make a mistake. Our great vessels and our skilful captains sometimes get lost in the wide ocean; but these little birds always know the way, and arrive with unerring certainty at their place of destination.
"Our great poet, Bryant, has written some beautiful lines to a water-fowl, which express this idea. I will repeat these lines to you if you like to hear them.
'Whither, 'midst falling dew,
While glow the heavens with the last steps of day,
Far, through their rosy depths, dost thou pursue
Thy solitary way?
Vainly the fowler's eye
Might mark thy distant flight to do thee wrong,
As, darkly limned upon the crimson sky,
Thy figure floats along.
Seek'st thou the plashy brink
Of weedy lake, or marge of river wide,
Or where the rocking billows rise and sink
On the chafed ocean side?