The big projectile was housed in the shed where it had been constructed, and the professor and the boys were working over it there, carefully guarded from curious eyes, for the German inventor did not want the secret of his Cardite motor to become known.
The work went on from day to day, good progress being made. The boys were of great assistance, for they were practical mechanics, and had had considerable experience.
"Well, I shall try the Cardite motor to-morrow," announced Professor
Roumann one night, after a hard day's work on the projectile.
"Do you think it will work?" asked Mr. Henderson.
"I think so, yes. My experiments have made me hopeful."
"And if it does work, when can we start?" asked Jack.
"Two days later; that is, if everything else is in readiness, the food and other, supplies on board."
"They are all ready to be stowed away," said Andy Sudds, who had been hunting all day.
It was an anxious assemblage that gathered inside the big shed the next day, to watch Professor Roumann try the Cardite motor. Would it work as well as had the Etherium one? Would it send them along through space at enormous speed? True, they would not have to travel so far, nor so fast, but more power would be needed, since, as it was feared no food, water, nor air could be had on the moon, many more supplies were to be taken along than on the trip to Mars, and this made the projectile heavier.
"We will test the Cardite in this small motor first," said Mr. Roumann, as he pointed to a machine in the projectile used for winding a cable around a windlass when there was necessity for hauling the Annihilator about, without sending it into the air.