"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 Mälar toward the Södertelje Canal. Birger and Gerda explored the boat, making friends with some of the passengers, and then found seats with Erik on the forward deck, where they could see the wooded shore of the lake. They passed many an island with its pretty villas peeping out among the green trees, and saw gay pleasure parties sailing or rowing on the quiet water. In a short time the boat sailed slowly into the peaceful waters of the Södertelje Canal. This is the first of the short canals which form links between the lakes and rivers of Southern Sweden, thus making a shorter waterway from Stockholm to Göteborg; and while the trip is about three hundred and seventy miles long, only fifty miles is actual canal, more than four-fifths of the distance being covered by lakes and rivers, with a fifty-mile sail on the Baltic Sea. The principal difficulty in making this waterway across Sweden lay in the fact that the highest of the lakes is about three hundred feet above the sea level, and the boats have to climb up to it from the Baltic Sea, and then climb down to Göteborg. This climbing is accomplished by means of locks in the canals between the different lakes. In some canals there is only one lock, but in others there are several together, like a flight of stairs. There are seventy-six locks in all. The boat sails into a lock and great gates are closed behind it. Then water pours in and lifts the boat slowly higher and higher until it is on a level with the water in the lock above. The gates in front of the boat are opened, it sails slowly into the next lock, the gates close behind it; and that lock in turn is filled to the level of the one above. The boat now wound along between the high green banks of the Södertelje Canal until it entered the first of the locks. Birger and Erik ran to the rail to watch the opening and closing of the gates, and the lowering of the boat to the level of the Baltic Sea; but Gerda preferred to talk with some old women who came on board with baskets full of kringlor,--ring-twisted cakes. The cakes looked so good, and everyone who bought them seemed to find them so delicious, that at last she ran to ask her father for some money; and when the boat had passed the lock and was once more on its way, she presented a bagful of cakes to Birger and Erik.