“The principle is parallel to that of an artillery shell that only bursts when it strikes, and might be extremely useful in warfare, if properly developed—­as I haven’t had time, yet, to develop it.  No matter about that, though.  My proposal has been rejected.  Peace having been declined, we have no alternative but to use other, means.  There is positively no way of coming to an agreement with our Moslem friends, below.”

As if to corroborate his statement, a rifle-bullet whistled through the open trap and flattened itself against the metal underbody of the fuselage, over their heads.  It fell almost at “Captain Alden’s” feet.  She picked it up and pocketed it.

“My first bit of Arabia,” said she.  “Worth keeping.”

The firing, below, had now become more general than ever.  Shrill cries rose to Allah for the destruction of these infidel flying dogs.  The Master paid no more heed to them than to the buzzing of so many bees.

“I think, Major,” said he, “we shall have to use one of the two kappa-ray bombs on these Arabic gentry.  It’s rather too bad we haven’t more of them, and that the capsules are all gone.”

“Pardon me, my Captain,” put in Leclair, “but the paralysis-vibrations, eh?  As you did to me, why not to them?”

“Impossible.  The way we’re crippled, now, I haven’t the equipment.  But I shall nevertheless be able to show you something, Lieutenant.  Major will you kindly drop one of the kappa-rays?”

He gestured at two singular-looking objects that stood on the metal floor of the lower gallery, about six feet from the trap.  Cubical objects they were, some five inches on the edge, each enclosed in what seemed a tough, black, leather-like substance netted with stout white cords that were woven together into a handle at the top.

Strong as Bohannan was, his face grew red, with swollen veins in forehead and neck, as he tried to lift this small object.  Nothing in the way of any known substance could possibly have weighed so much; not even solid lead or gold.

“Faith!” grunted the major.  “What the devil?  These two little metal boxes didn’t weigh a pound apiece when—­ugh!—­when we packed ’em in our bags.  How about it, chief?”

The Master smiled with amusement.

“They weren’t magnetized then, Major,” he answered.  “Shall I have someone help you?”

“No, by God!  I’ll either lift this thing or die, right here!” the Celt panted, redder still.  But he did not lift the little cube.  The best he could do was to drag it, against mighty resistance, to the edge of the trap; and with a last, mighty heave, project it into space.

As it left the trap, Nissr rocked and swayed, showing how great a weight had been let drop.  Down sped the little, netted cube, whirling in the sunlight.  Its speed was almost that of a rifle-ball—­so far in excess of anything that could have been produced by gravitation as to suggest that some strange, magnetic force was hurling it earthward, like a metal-filing toward an electro-magnet.  It dwindled to nothing, in a second, and vanished.