"Quite sure. But we will have a test to make certain. Send Professor Henderson here, Please."
The other scientist came from the house, and the test was made. To the delight of all the Etherium motor worked perfectly. The slight adjustment of the piece of metal had been all that was needed.
"Now we can get ready to leave in a week," repeated the German enthusiastically.
In fact, the projectile was finished, and all that was necessary was to put in the stores and some supplies, turn on the power, and they would be off through space.
The actual starting of the Annihilator was, of course, to be left entirely to Mr. Roumann. He had not disclosed to his companions the secret of the force that was to make it move, nor had he told them how to work the Etherium and atmospheric motors. He would start the machinery in operation, and he had promised to show the professor and the boys how to control it, but the secret of the wonderful power he kept to himself.
"I think we can let the two machinists go now," said Mr. Henderson at the conclusion of the tests. "We shall not need them any more if we are almost ready to start."
"No, we can dispense with their services," agreed Mr. Roumann; and, accordingly, Ned and Sam were paid off, and left, promising to say nothing of the wonderful apparatus on which they had been working.
The next week was a busy one. Mr. Roumann spent most of his time in the engine–room, assembling the machinery of the two motors, and arranging the connections between them and the pilot house in the "nose" of the projectile. The strange gas had been forced in between the two shells of the projectile, to absorb the heat that would be generated by friction, and nearly all the stores had been put aboard.
The electric guns were installed, ready to be run out of the openings of the living–room to repel any attack of the Martians, and then the ports were closed tightly.
Finishing touches were being put on the Annihilator, and Mr. Henderson and his German friend were kept very busy. As for the boys, they helped wherever they could, and did considerable work, for they had been well trained by their guardian.