“But, Father,” cried Birger, “Goeteborg is a long way from Stockholm!  How can Erik go so far alone?”

“I am going over to Goeteborg myself next month,” replied Inspector Ekman, “and he can go with me.  A new lightship is ready to be launched, and I shall have to inspect it and give the certificate before it is accepted by the government.”

“Let us go with you!  Let us go, too!” begged the twins, dancing round and round their father.

“But what will become of Karen?” he asked.

Gerda and Birger stopped short and looked at their new friend.  It was plain to be seen that she was not strong enough to take such a trip.

Fru Ekman put her arm tenderly around the little lame girl.  “Karen will visit me,” she said kindly.

So it was decided that the twins should go to Goeteborg with their father by way of the Goeta Canal.  When the day for the journey arrived, the satchels were packed once more, and Gerda showed Karen how to water her plants and feed her pet parrot in her absence.

CHAPTER XI

THROUGH THE LOCKS

“What do you think of a girl who goes off on two journeys in one summer?” and Gerda leaned over the railing of the canal-boat to look at her friends on the quay below.

It was the middle of August, and the same group of boys and girls who had seen the twins off to the North in June were now speeding them to the West.

“I think you don’t care for Stockholm any longer,” called Hilma; while Oscar added, “And you can’t care for your friends either, or you wouldn’t be leaving them again so soon.”

“I shall be home in just seven days,” said Gerda, “and if you will all be here on the quay to welcome me, I will tell you the whole story of the wonderful Goeta Canal, and our sight-seeing in Goeteborg.”

“Your friends will have to meet you at the railroad station,” her father told her.  “We shall come back by train.  It is much the quickest way.”

“At the railroad station then, one week from to-day,” called Gerda, as the steamer backed away from the quay, and swung slowly out into the Maelar Lake.

“Gerda and Birger are the luckiest twins I know,” exclaimed Olaf, taking off his cap and swinging it around his head, as he caught sight of Gerda’s fluttering handkerchief.

“That boy Erik seems to be very fond of Birger,” said Oscar.  “And now that the little girl from the lighthouse is going to live with the Ekmans this winter, I suppose the twins will forget all the rest of us.”

“Nonsense!” exclaimed Sigrid loyally.  “They will never forget their friends.  Besides, I like Karen myself.  Let’s go and see her now.  She must be lonely without Gerda.”

In the meantime the little party of four—­Lieutenant Ekman, with Erik and the twins—­were sailing across the eastern end of Lake Maelar toward the Soedertelje Canal.