"Why didn't they build fortifications on the islands and hold the enemy at bay?" questioned Birger.

"They were too busy sailing off to foreign lands," answered his father. "Fleet after fleet of Viking ships sailed out of the bays of Sweden, manned by the bravest sailors the world has ever known; and they swooped down upon the tribes of Europe, fighting and conquering them with the strength of giants and the glee of children."

"It was Birger Jarl who built the first walls and towers to protect the city," spoke Gerda. "I remember learning it in my history lesson."

"Yes," her father replied; "good old Earl Birger, who ruled the Swedes in the thirteenth century, saw how important such fortifications would be, and so he locked up the Mälar Lake from hostile fleets by building walls and towers around one of the islands and making it his capital."

"There is an old folk-song in one of my books which always reminds me of the Vikings," said Birger.

"Let us hear it," suggested his father, and Birger repeated:—

"Brave of heart and warriors bold,
Were the Swedes from time untold;
Breasts for honor ever warm,
Youthful strength in hero arm.
Blue eyes bright
Dance with light
For thy dear green valleys old.
North, thou giant limb of earth,
With thy friendly, homely hearth."

"There is another stanza," said Gerda. "I like the second one best," and she added:—

"Song of many a thousand year
Rings through wood and valley clear;
Picture thou of waters wild,
Yet as tears of mourning mild.
To the rhyme
Of past time
Blend all hearts and lists each ear.
Guard the songs of Swedish lore,
Love and sing them evermore."

"Good," said Lieutenant Ekman; "isn't there a third stanza, Birger?"