"I'm afraid it's too dark out there now. But I should be delighted to show it to you if you care to come again, during the daytime." "Oh, I'd love to. Thank you so--Oh, what's that noise?" Anna looked at Greta, whose face had turned white. She, too, had heard a most unusual sound. "I didn't hear any noise," said Mr. Christianson. "It sounded like heavy wooden wheels," said Greta, who looked quite scared. "It couldn't be that, Greta," said Hans. "No one has come into the courtyard." "But I heard them _inside_ the castle," insisted Greta. "Oh, of course. I had forgotten." Then Mr. Christianson explained. "A long time ago, when this castle was first built, the entrance to the courtyard was in the center of this building, instead of at the side, as it is now. In fact, this drawing-room was built where the entrance used to be. Up to the very day of his death, the old coachman never approved of this change. So every evening, about this time, he drives his coach and four over the old road and through the old entrance. He has to come right through this room and that is why you always hear him." The two girls looked at Mr. Christianson in wonder. "You mean his _ghost_ drives through here every evening?" asked Greta. "Yes, Greta." "But I didn't think there were any _real_ ghosts," said Anna. "I don't know, my dear. No one has ever _seen_ him, but you yourself heard the rumble of the wooden wheels of the coach just now." "I certainly heard _something_," admitted Anna. "What else could it be?" asked Hans, who was delighted to hear Anna admit even this much. On the way home from Vosborg, Anna was very quiet. Finally she just had to ask, "Tante Agnes, do _you_ think that was the old coach that we heard tonight?" Her aunt smiled. "I don't know, Anna. I think you had better go to Vosborg again in the daytime. Then you can find out for yourself whether or not it has any ghosts." CHAPTER VII A DAY AT THE SHORE "Why don't you have a windmill on your farm, Uncle Frederick?" asked Anna. "Every one of these farms has a big windmill." Anna and her uncle and Greta were driving through the country on their way to the shore. Greta's father had to make a business trip to a small town on the coast, and he was taking the girls with him. Chouse was comfortably curled up on the back seat. "We don't need a windmill, Anna, because we have the river." "But how can the river take the place of a windmill?" asked Anna. [Illustration: THE WINDMILLS PROVIDE ELECTRIC POWER] "Greta, haven't you shown Anna the dam in the river?" asked her father. "This dam causes the water to fall from a great height. The force of the water, as it falls on a large machine, provides the power that is turned into electricity. These other farms get their electric power from the windmills. As the great arms are turned by the wind, they provide power that is changed, by the machinery, into electricity."