"You can take us back, sir," said Popham, who had been pacing the floor nervously. "Shut off the power of this infernal machine and let us drop back to where we belong. Two miles is no great matter. Your castle is a slow freight compared with some of Gilhooly's express trains."

"I cannot take you back, sir," returned the professor, "and I would not if I could. You did not hear me out. The law of velocity, recited for your benefit a moment ago, does not measure the speed of this car."

"No?" murmured Markham.

"Decidedly not. The earth sweeps along in its orbit at the rate of eighteen miles to the second, while some aerolites and meteoroids attain a speed of twenty and thirty miles to the second. In building this car, I equipped it with an anti-gravity block geared up to fifty miles to the second. The lever on the wall"—and here Quinn turned and pointed to it—-"is thrown so as to give us the maximum."

"In other words," said Popham feebly, "we are sailing skyward at a rate of—of three thousand miles per—per minute?"

"Presumably. As we left my city lot in New York at about eleven-fifteen, it follows that we have been one hour on the way."

"And should be one hundred and eighty thousand miles from home," faltered Meigs.

"About that," answered the professor calmly. "I do not know just how much our progress was impeded by the atmospheric envelope of the earth, but I think we may call our distance from the mother orb some one hundred and eighty thousand miles, in round numbers."

These startling figures came near to unsettling the three gentlemen again. In that flight through space we were confronting immensities well-nigh beyond our puny comprehension. And the professor was not yet done.

"In the storeroom overhead," he continued, "I have a supply of cubes and insulating compound which I can combine and give tremendous added velocity to the car."