“With their good-for-something father,” cried Gerda, throwing her arms around his neck and giving him a loving kiss.

“Am I really good for something?” he asked, as soon as he could speak.  “Well then, you must be good for something, too.  In olden times the Vikings sailed the seas and brought home many a treasure from foreign shores.  See that you take home some treasures from your journey,—­something that will remind you of the towns we visit and the sights we see,” and he put his hand into his pocket and took out three coins.

“The Vikings had a fashion of taking what they wanted without paying for it,” suggested Birger.

“You’d better not try it now, my son,” replied Herr Ekman; and he gave each one of the children a krona.

“Here’s a kringla to remind me of Soedertelje,” said Gerda, slipping one of the cakes into her pocket; and then the three children went off to the forward deck to watch the boat sail out into the ocean.

For fifty miles they sailed among wooded islands and rocky ledges, and then entered the canal which connects the Baltic Sea with Lake Roxen.  On the way the boat stopped at two or three ports, and each tune the children went ashore to buy a souvenir.

“Show me your treasures, and I will show you mine,” Gerda said to Erik, after the first stop.

The boy shook his head.  “I bought something useful,” he said, “and I shall send it to my father;” but even with coaxing he would not tell what it was, until they were all ready to show their treasures to Lieutenant Ekman.  So all three of the children agreed to keep their souvenirs a secret, and had great fun slipping off alone to buy them.

All day and all night, and all the next day, the boat steamed across the open lakes, glided noiselessly into the quiet canals, or climbed slowly step by step up the locks.

Toward night of the second day Birger suddenly announced, “This is Lake Viken, and it is the highest lake on the way between the two ends of the canal route.  The captain says that it is more than three hundred feet above the level of the sea.”

“Have we seen the prettiest part of the route?” asked Gerda.

“Far from it,” was the answer.  “The best part of the canal is still before us, at Trollhaettan, although the next lake that we enter, Lake Vener, is a lovely sheet of water.  It is the largest lake in Sweden, and I must visit one of the lighthouses.”

“And I must call upon one of the trolls when we get to Trollhaettan,” said Gerda, shaking her head with an air of importance.

“I shall walk up the locks,” said Birger.

“You mean that you will walk down the locks,” Erik corrected him.  “After this the boat will go downstairs until we reach the Goeta River.”

And when, on the last morning of the journey, they reached Trollhaettan, with its famous waterfalls and rapids, the children went ashore and left the boat to walk down the steep hillside by itself, while they ran along beside the canal, or took little trips through the groves to get a better view of the falls.  Gerda peered under the trees and bushes for a glimpse of the water witches, but she saw not one.