e of
course," and started for the front door. "Only I must say it's behaving
mighty queer."

But when they opened the door and looked out into the rocky road there
was no sign of an automobile, and yet the humming sound still kept on.

As they listened, wide-eyed, the noise grew softer and softer and
gradually died away in the distance.

The girls looked at each other wonderingly. Then it was Billie who
offered a solution.

"Mightn't it be an aeroplane?"

"An aeroplane in this part of the country?" Laura was inclined to scoff
at the idea, but Mrs. Gilligan and Violet both stood up for Billie.

They were about to enter into a heated argument when they saw the wagon
that had by this time become familiar to them coming down the road with
the boys seated in it or hanging to it in characteristic attitudes.

The girls ran out to them and deluged the lads with questions before they
had time to learn what it was all about.

"A motor car?" asked Chet. "No, we didn't pass a soul on the way up
here."

When the girls had poured into their interested ears the story of the
queer humming sound that had just repeated itself, they agreed to one man
to Billie's suggestion that it was very probably an aeroplane.

"I'll tell you what we'll do next time we hear it," said Teddy as the
boys picked up the provisions they had brought and started toward the
house. "We'll go up on the roof. Then we'll pretty soon see whether it's
a ghost or the real thing."

"And in the meantime," suggested Chet, sniffing the air hungrily, "how
about some supper?"

CHAPTER XXI

BOTH AT ONCE

It was not long before there came a recurrence of the strange humming
noise which had so disturbed the girls. It was only a few nights later
that Chet sat up in bed with the joyful feeling that here at last was a
chance to investigate at least one of the ghosts that haunted the
homestead at Cherry Corners.

"Ferd! Teddy! Wake up! What's the matter? Are you dead?" he called
to the boys.

The latter reluctantly opened their eyes and looked at him reproachfully.

"Can't you let a fellow sleep?" Teddy asked. But Chet, with no ceremony
whatever, hauled him bodily out of bed and set him on his feet.

"Don't talk," he ordered. "Run as fast as you can to the roof before
we miss it."

"What are you raving about?" asked Ferd, although both he and Teddy
started obediently toward the attic stairs.

"If you wouldn't talk so much, you could hear it," Chet