Chapter Eighteen. The Electric Gun

There was much excitement aboard the Advance. The submarine came to a stop in the water, while the treasure- seekers waited anxiously for what was to follow. Would they be rammed again? This time, stationary as they were, and with the other boat coming swiftly on, a hole might be stove through the Advance, in spite of her powerful sides.

They had not long to wait. Again there came a jar, and once more the Swifts' boat careened. But the blow was a glancing one and, fortunately, did little damage.

"They certainly must be trying to sink us," agreed Captain Weston. "Come, Tom, we'll take a look from the stern and see what they're up to."

"And get the stern electric gun ready to fire," repeated Mr. Swift. "We must protect ourselves. Mr. Sharp and I will go to the bow. There is no telling what they may do. They're desperate, and may ram us from in front"

Tom and the captain hurried aft. Through the thick plate- glass windows they could see the blunt nose of the Wonder not far away, the rival submarine having come to a halt. There she lay, black and silent, like some monster fish waiting to devour its victim.

"There doesn't appear to be much damage done back here," observed Tom. "No leaks. Guess they didn't puncture us."

"Perhaps it was due to an accident that they rammed us," suggested the captain.

"Well, they wouldn't have done it if they hadn't followed us so close," was the opinion of the young inventor. "They're taking too many chances. We've got to stop 'em."

"What is this electric gun your father speaks of?"

"Why, it's a regular electric cannon. It fires a solid ball, weighing about twenty-five pounds, but instead of powder, which would hardly do under water, and instead of compressed air, which is used in the torpedo tubes of the Government submarines, we use a current of electricity. It forces the cannon ball out with great energy."

"I wonder what they will do next?" observed the captain, peering through a bull'seye.

"We can soon tell," replied the youth. "We'll go ahead, and if they try to follow I'm going to fire on them."

"Suppose you sink them?"

"I won't fire to do that; only to disable them. They brought it on themselves. We can't risk having them damage us. Help me with the cannon, will you please, captain?"

The electric cannon was a long, steel tube in the after part of the submarine. It projected a slight distance from the sides of the ship, and by an ingenious arrangement could he swung around in a ball and socket joint, thus enabling it to shoot in almost any direction.

It was the work of but a few minutes to get it ready and, with the muzzle pointing toward the Wonder, Tom adjusted the electric wires and inserted