Within three minutes they were close enough to see a sky hold-up. A long cylinder, tremendously long it seemed to her as she viewed it through the fog, swung gracefully and easily into position over the Greyhound, and for several moments ran along smoothly as if it were a part of the lower airship. Then a trap door opened in the bottom of the cylinder, a rope fell into the aviator’s seat of the Greyhound, and ten men descended quickly. For several seconds the ladder swung to and fro over the Greyhound but when a signal whistle, sharp and clear, rang out from the aviator’s seat of the Greyhound, the great cylinder whirled with lightning speed and darted away directly north. It was swallowed up so quickly in the fog that Joan could only stare at it with open-mouthed surprise.
When she thought to look back at the Greyhound the captured vessel had swung into the course of the cylinder.
“It is impossible to follow that thing,” she whispered in awe. “Why it flies—it flies—like—like——”
“A ball out of a cannon,” Epworth finished. “But fortunately I did not contemplate following it. We will follow the Greyhound. I knew before we started out on this trip that those cylinders could gain a speed of six hundred miles an hour, and my plot was to get them to capture the Greyhound, and follow it. They have fallen into the plot, and now a sky bandit, and not Billy, is piloting the plane.”
With a careful movement he dropped in behind the Greyhound, and climbed up over it. But presently he discovered that he would have to go higher. The Greyhound was gradually seeking altitude in a long upward nose sweep. This movement was continued until an altitude of five thousand feet had been attained. At this altitude the Greyhound leveled out, put on more speed, and darted courageously toward the frozen North. Epworth followed, easily keeping the three red lights in view although the cut-out of the Greyhound was now closed.
“Six hundred miles an hour!” Joan’s voice contained an element of doubt. “How could they attain such a speed? There is no known force that will pull them that fast.”
“Goddard’s liquid rockets,” Epworth answered briefly. “I was studying their explosion when the hold-up was taking place. They have a soft, low, whirling explosion but these men have gone the scientist one better. They have found a method of silencing the explosions and still retaining all the force.”
“My, I wonder where they are taking the Greyhound?”
“We are following them to find out.”
“I am still wondering how the cylinders can give such speed.”