operator could guide the machine in any direction he desired, and
he could also regulate the rate of progress.

A number of scientific instruments were carried, for showing and
registering the speed and direction of the Annihilator, the
distance it was above the earth, and there was an indicator to
note how near the travelers came to Mars. There was also a
powerful telescope, and a number of cameras so arranged that they
would automatically take pictures.

"We'll have to travel through space pretty fast in order to cover
thirty-five millions of miles," observed Jack, stopping in his
work of helping rivet some of the plates.

"About how fast will we have to go, Mr. Roumann?"

"I have it all figured out," replied the German.

"I hope our projectile will stand it," remarked Mr. Henderson.
"We did not have to make such terrific speed on our other
voyages."

"I think that the Annihilator, as we have planned it, will not
suffer from the strain of speed," when on Mr. Roumann, looking up
from his study of some blue-prints. "You may be astonished when
I tell you we shall have to travel at the rate of one hundred
miles a second."

"One hundred miles a second!" exclaimed Jack. "That's pretty
fast, isn't it?"