“They had a gun on the West Front⁠—a seventy-five,” said O’Keefe, “that broke the eardrums of everybody who fired it, no matter what protection they used. It looked like all the other seventy-fives⁠—but there was something about its sound that did it. They had to recast it.”

“It’s practically the same thing,” I replied. “By some freak its vibratory qualities had that effect. The deep whistle of the sunken Lusitania would, for instance, make the Singer Building shake to its foundations; while the Olympic did not affect the Singer at all but made the Woolworth shiver all through. In each case they stimulated the atomic vibration of the particular building⁠—”

I paused, aware all at once of an intense drowsiness. O’Keefe, yawning, reached down to unfasten his puttees.

“Lord, I’m sleepy!” he exclaimed. “Can’t understand it⁠—what you say⁠—most⁠—interesting⁠—Lord!” he yawned again; straightened. “What made Reddy take such a shine to the Russian?” he asked.