"I never heard that there was much gold on Mars," said Jack.

"Not in the form of gold," said the German, who was growing very
excited, "but something that can be turned into gold. I am on
the track of the most wonderful substance--that which gives Mars
its red color--that which will--"

He stopped suddenly.

"I must say no more now," he added, calming himself by a strong
effort. "Sufficient to state that you will never regret making
the trip to the wonderful planet."

"But now about your new force--how powerful is it?" asked Mr.
Henderson. "You promised to demonstrate it to me."

"Yes, and I will do so."

Thereupon the German plunged into a mass of figures and
calculations, which were quite puzzling to the boys, but which
seemed very clear to Mr. Henderson. The German drew several
rough outlines, and the discussion became quite technical. Toward
the close, the inventor of the-secret force gave a demonstration
of its power. By means of certain chemicals and an electric
current he developed from the end of a wire a force sufficient to
knock over a heavy block of steel, weighing over a ton.

"That is only a small sample of what my force will do," he said.
"In the proper machine it will be ten times more strong. The
conditions here are not exactly harmonious. Now, are you