"I can remember it well," continued Claude Ranworth. "It was about three o'clock in the morning. The sun was obscured, and overhead was a bank of heavy clouds. I saw a vivid flash reflected on the underside of the clouds, followed by a dull report. The interval between the flash and the report was seventy seconds according to my calculation, for I had no watch available."
"You were always pretty good at counting seconds," remarked Ranworth. "Then what happened?"
"A heavy cloud of smoke drifted in this direction. It hung about for nearly two hours before it finally dispersed."
"Can you indicate the actual direction of the flash?"
"Yes," replied Claude. "Do you see that hummock with a peculiar double crown? If you stand in front of the second hut from here, the crest of the hummock is practically in line with the place from which the flash emanated. But why are you so interested, Jack?"
"Because," said John Ranworth, "I have every reason to believe that the flash you saw was the explosion of the airship in which these Russians had been travelling."
Claude Ranworth made a gesture of annoyance.
"I thought I had observed an unusual seismic disturbance," he cried. "In fact, I immediately entered a detailed description of a supposed volcanic eruption in my log, meaning to send a report to the Royal Society. By the bye, that reminds me; if anything should happen to me during your absence, my scientific documents—I'm afraid I haven't kept them up-to-date—are under my sleeping bag. But I'm awfully sorry it wasn't an earthquake."
"So am I," agreed Ranworth. "It might have saved me a long journey."
He snatched up a piece of paper lying on the cabin table and worked out a short sum. Seventy seconds was the time given by Claude as having elapsed between the flash and the detonation. Allowing sound to travel at 365 yards a second, the distance worked out at just over fourteen miles.