I'll turn on the power gradually now, and we'll see what happens."

"How fast do you think it ought to send us along?" asked Jack.

"Oh, perhaps one hundred and twenty-five miles a second. You know we
went a hundred miles a second when we headed for Mars. I would not be
surprised if we made even one hundred and thirty miles a second with
the Cardite."

"Whew! If we ever hit anything going like that!" exclaimed old Andy
Sudds.

"We'd go right through it," finished Jack fervently. The professor was
soon ready for the test. Slowly he shoved over the controlling lever.
The Cardite motor hummed more loudly, like some great cat purring.
Louder snapped the electrical waves. The air vibrated with the enormous
speed of the valve wheels, and there was a prickling sensation as the
power flowed into the positive and negative plates, by which the
projectile was moved through space.

"Watch the hand of the speed indicator, boys," directed Professor
Roumann, "while Professor Henderson and I manipulate the motor. Call
out the figures to us, for we must keep our eyes on the valves." Slowly
the speed indicator hand, which was like that of an automobile
speedometer, swept over the dial.

"Fifty miles a second," read off Mark. The two professors shoved the
levers over still more.

"Seventy-five," called Jack.