was a perceptible increase to the speed of the Advance.
"Are we leaving them behind?" asked Tom anxiously, as he glanced at the speed gage, and noted that the submarine was now about five hundred feet below the surface.
"Hard to tell," replied the captain. "You'd have to take an observation to make sure."
"I'll do it," cried the youth. "You steer, please, and I'll go in the conning tower. I can look forward and aft there, as well as straight up. Maybe I can see the Wonder."
Springing up the circular ladder leading into the tower, Tom glanced through the windows all about the small pilot house. He saw a curious sight. It was as if the submarine was in a sea of yellowish liquid fire. She was immersed in water which glowed with the flames that contained no heat. So light was it, in fact, that there was no need of the incandescents in the tower. The young inventor could have seen to read a paper by the illumination of the phosphorus. But he had something else to do than observe this phenomenon. He wanted to see if he could catch' sight of the rival submarine.
At first he could make out nothing save the swirl and boiling of the sea, caused by the progress of the Advance through it. But suddenly,
