Professor Roumann made a strange proposition. He said if the old scientist and his young friends would build the proper kind of a projectile, they could make a trip to the planet Mars, by means of a wonderful motor, operated by a power called Etherium, of which Mr. Roumann held the secret. After some discussion, the projectile, called the _Annihilator_, from the fact that it annihilated space, was begun. It was two hundred feet long, ten feet in diameter in the middle, and shaped like a cigar. It consisted of a double shell of strong metal, with a non-conducting gas between the two sides. Within it were various machines, besides the Etherium motor, which would send the projectile along at the rate of one hundred miles a second. This great speed was necessary in order to reach the planet Mars, which, at the time our friends started for it, was about thirty-five millions of miles away from this earth. It has since receded some distance farther than this. Finally all was in readiness for the start to Mars. Professor Roumann wanted to prove that the planet was inhabited, and he also wanted to get some of a peculiar substance, which he believed gave the planet its rosy hue. He had an idea that it would prove of great value. But, though every precaution was taken, the adventurers were not to get away from the earth safely. Almost at the last minute, a crazy machinist, named Fred Axtell, who was refused work on the projectile, tried to blow it up with a bomb. He partly succeeded, but the damage was repaired, and the start made. Inside the projectile our friends shut themselves up, and the powerful motors were started. Off it shot, at the rate of one hundred miles a second, but the travellers were as comfortable as in a Pullman car. They had plenty to eat and drink, they manufactured their own air and water, and they slept when they so desired. But Axtell, the crazy machinist, had hidden himself aboard, and, in mid-air, he tried to wreck the projectile. He was caught, and locked up in a spare room, but, when Mars was reached, he escaped. The book tells how our friends were welcomed by the Martians, how they learned the language, saw many strange sights, and finally got on the track of the Cardite, or red substance, which the German professor, Mr. Roumann, had come so far to seek. This Cardite was capable of great force, and, properly controlled, could move great weights and operate powerful machinery. Our friends wanted to take some back to earth with them, but when they attempted to store it in their projectile, they met with objections, for the Martians did not want them to take any. They had considerable trouble, and the crazy machinist led an attack of the soldiers of the red planet against our friends, the adventurers in the projectile.