Again, between high heaven's black vault and the fantastic continent of cloud below, nothing remained but free vacancy.

The Master smiled.
"Vibrations, my dear Major!" said he.

"Neutralize the currents delivered by the magnetos of hostile planes to their spark-plugs, and you transform the most powerful engines into inert matter.

Not all the finely adjusted mechanism in the world, nor the best of petrol, nor yet the most perfect skill is worth _that_," with a snap of the strong fingers, "when the spark dies.
"My device is the absolute ruler of whatever spark I direct it against.

Our own ignition is screened; but all others within the critical radius become impotent.