"Get the spade and try," ordered Darry. "If you don't find some
bait we'll have to put off fishing until some other day."

That brought Dan to terms. He shouldered a spade, picked up an
empty vegetable can and started away, while Dave began to sort
tackle and to rig on hooks suitable for catching perch. Tom and
Harry started in to unpack supplies from a pair of six-quart pails
that they needed for the morning's work.

"Say, hear that, fellows!" demanded Tom, straightening up suddenly.

From the distance to the northward came a dull rumbling sound.

"Thunder?" suggested Danny Grin, glancing wonderingly up at the
clear sky.

"If there's a storm coming it will upset a day's berrying," Reade
announced.

"Fellows," Dick broke in, "it's a rumbling, yet it doesn't sound
just like thunder, either. It sounds more like-----"

"Cavalry on a gallop," suggested Greg.

"Just what it does sound a lot like," Prescott nodded. Then he
dropped to the ground, holding one ear close to the earth.

"And, whatever the rumble may be," Prescott went on, "it travels
along the ground. Just get your ears down, fellows."