"Nothing will happen. Look out now, I'm going to fire."
The guns were to be fired simultaneously by means of an electric current, when Tom pressed a button.
"Here they go!" exclaimed the young inventor.
There was a moment of waiting, and then came a thundering roar. The Mars trembled, but she did not shift to either side from an even keel. From one barrel of the guns shot out the explosive projectiles, and from the other spurted a jet of water, sent out by a charge of powder, equal in weight to that which forced out the shot.
As the projectile was fired in one direction, and the water in one directly opposite, the two discharges neutralized one another.
Out flew the pointed steel shells, to fall harmlessly into the sea, where they exploded, sending up columns of water.
"Well!" cried Tom as the echoes died away. "How was it?"
"Couldn't have been better," declared Lieutenant Marbury. "There wasn't the least shock of recoil. Tom Swift, you have solved the problem, I do believe! Your aerial warship is a success!"
"I'm glad to hear you say so. There are one or two little things that need changing, but I really think I have about what the United States Government wants."
"I am, also, of that belief, Tom. If only—" The officer stopped suddenly.