He dropped to his knees, while Simmonds lighted him, and I saw that there was a hole in the floor about three inches in diameter.  Godfrey felt carefully about it for a moment, and then, with a little exclamation of triumph, found a hold for his fingers, pulled sharply, and raised a hinged section of the floor, about eighteen inches square.

“Now give us the light,” he said, and plunged it into the opening.

In line with the little hole was an upright metal tube about a foot long, ending in a small square box.  Beside the tube, a slender iron rod ran from the platform down into the box.

“That’s the lever that sets it off,” remarked Godfrey, tapping the rod.  “A pressure of the foot did it.”

He pulled the rod loose, seized the tube, and lifted the whole apparatus out upon the platform.

“Let’s take it down where we can look at it,” he said, and, carrying it easily in one hand, led the way back to the library, cleared a place on the table and set it down.  Then, after a moment’s examination, he pulled back a little bolt and tilted the top of the box, with the tube attached, to one side.

A curious mechanism lay revealed.  There was a powerful spring, which could be wound up with a key, and a drum wound with filament-like wire and connected with a simple clock-work to revolve it.  Two small dry-batteries were secured to one side of the box, their wires running to the drum.

“Why, it’s nothing but a toy catapult!” I said.

“That’s all,” and Godfrey nodded.  “It remained for Silva to add a few trimmings of his own and to put it to a unique use.  Instead of a missile, he loaded it with his little aerial shell, attached to the end of this wire.  Then he shot it off with a pressure of the foot; when it reached the end of the wire, the pull brought this platinum coil against the battery wires and closed the circuit.  The spark fired the shell, and the drum began to revolve and pull it down.  That explains, Lester, why it descended so steadily and in a straight line.  The fellow who could devise a thing like that deserves to succeed!  Here’s health to him!”

“He ought to be behind the bars,” growled Simmonds.  “The cleverer he is, the more dangerous he is.”

“Well,” retorted Godfrey, “I admire him, anyway; and he isn’t behind the bars yet.  No doubt you’ll find some of his shells to-morrow about the house somewhere, and you might amuse yourself by shooting one off every night at midnight, on the chance that he sees it and comes back to see who’s stealing his thunder!”

But this brilliant suggestion didn’t seem to appeal to Simmonds, who merely grunted and continued his examination of the catapult.

“Silva had loaded it for to-night’s performance,” Godfrey went on, “but, as I remarked before, the leading lady failed to answer her cue, and it remained for us to touch it off.  There it is, Simmonds; I turn it over to you.  It and the glove will make unique additions to the museum at headquarters.  And now,” he added, with the wide yawn of sudden relaxation, “you fellows can make a night of it, if you want to, but I’m going to bed.”