"That was right," commended Tom. "Well, try reversing. It can't do any harm, and it may make it easier for us to free the propellers when we go out."
He went to the engine room himself to see that everything was properly attended to. Slowly the motors were reversed, and only a slight current was given them, as, with the resistance of the tightly wound weed, too powerful a force might burn out the insulation.
Slowly the starting lever was thrown over. There was a low humming and whining as the current jumped from the batteries, and a slight vibration of the craft. Tom looked at the movable pointer which showed the speed and direction of the propellers. The hand oscillated slightly and then stopped.
"Shut off the current!" cried Tom. "It's of no use. The propellers are held as tight as a drum! We've got to go out and cut loose the serpent weed!"
The experiment of reversing the propellers had failed. But still Tom did not believe his craft was in danger. He gave orders for the engine room force to stand by and then arranged for himself, Ned, and Koku to go outside in diving dress and cut the weed off the shafts. There were twin propellers on the submarine, each revolving independently by separate motors, and each capable of being sent in forward or reverse direction.
"Start the engines as soon as we give the signal," Tom told the machinist. "Two knocks on the hull with an axe will mean go ahead, and three will mean reverse."
"I understand," said Weyth, the machinist. "But stand away from the propellers after you give the signal. I'll give you three minutes to move clear."
"That will be enough," Tom said. "But better make it half speed in either case. My idea is that if we can partly cut the weed off, starting the propellers, either forward or in reverse, will finish the trick."
"It may," agreed Weyth.
Armed with axes and sharp steel bars, Tom, Ned, and Koku were soon ready to step outside the submarine.