The only way was to come gradually down to the former speed, and, while
Mark kept his eyes on the indicator, Jack pulled the lever toward him,
notch by notch.

"She's down to seventy-five miles a second," whispered Mark. They were
as anxious now to reduce speed as they had been before to increase it.

Meanwhile Professor Roumann had set in motion a curious bit of
apparatus, designed to repel stray meteors or detached bits of comets.
As is well known, bodies floating in space, away from the attraction of
gravitation, attract or repel each other as does a magnet or an
electrically charged object.

Acting on this law of nature, Professor Roumann had, with the aid of
Mr. Henderson, constructed a machine which, when a negative current of
electricity was sent into it, would force away any object that was
approaching the _Annihilator_. In a few moments the boys at the
Cardite motor heard the hum, the throb and crackling that told them
that the repelling apparatus was at work.

But would it act in time? Or would the meteor prove too powerful for
it? And, if it did, would the two scientists be able to steer the
swiftly moving projectile out of the way of the big, black stone, as
the old hunter called it?

These were questions that showed on the faces of the two lads as they
bent over the motor.

"We're only going fifty miles a second now," whispered Jack.