“You’ve no business to get so close to the bridge,” the watchman retorted. “It’s agin’ the regulations. I could have you arrested.”
“But it wasn’t our fault this old sailboat upset,” Penny returned reasonably. “We were reaching for a floating bottle—oh, my Aunt! Where is that bottle, Louise? Don’t tell me we’ve lost it!”
Her chum was given no opportunity to reply, for at that moment a motorboat roared down the river at high speed. Its throttle was wide open, and it appeared to be racing straight toward the bridge.
“Halt!” shouted the watchman, jerking a weapon from a leather holster. “Halt!”
The pilot did not obey the command. Instead, to the amazement of the watchers, he leaped from the cockpit and swam for the opposite shore. Twice the watchman fired at him, but the bullets were well above the swimmer’s head.
The unpiloted boat, its helm securely lashed, drove straight on its course.
“It’s going to strike the bridge!” shouted Louise.
As the boat raced head on into one of the massive concrete piers, there came a deafening explosion. The entire steel structure of the bridge seemed to recoil from the impact. Girders shivered and shook, cables rattled. On the eastern approach, brakes screamed as automobiles were brought to a sudden halt.
“Saboteurs!” the watchman cried hoarsely. “They’ve done it—dynamited the bridge!”