The ice-boat was skimming down the lake, when there suddenly sounded a boom like the report of a cannon.
“What was that?” called Ned.
“The ice cracked,” Jerry answered. “It often does that after a thaw. I guess——”
“Look out!” yelled Bill. “There’s open water just ahead!”
A big crack had opened in the ice, just in front of the ice-boat, and before Jerry could steer to one side the Petrel plunged in.
“Jump!” yelled Jerry, casting aside the mainsheet.
As the boat splashed into the cold water the boys, leaping free of her, went in also, but on either side.
Jerry saw his two chums and Bill strike out as they hit the water, but he also had a glimpse of Bart throwing up his hands with a gesture of despair, and in a flash it came to Jerry.
“Bart can’t swim!”
The lad had so confessed some time ago, admitting he had a terror of being in the water, though not afraid to go out in a boat.