Kennedy’s mind was working rapidly in the crisis as Marlowe appealed to him, almost helplessly.

“May I have your car to-night?” asked Craig, pausing.

“Have it?  I’ll give it to you if it’ll do any good.”

“I’ll need it only a few hours.  I think I have a scheme that will work perfectly—­if you are sure you can guard the inside of the yard to-morrow.”

“I’m sure of that.  We spent hours to-day selecting picked men for the launching, going over everything.”

Late as it was to start out of town, Craig drove across the bridge and out on Long Island, never stopping until we came to a small lake, around the shores of which he skirted, at last pausing before a huge barn-like structure.

As the door swung open to his honking the horn, the light which streamed forth shone on a sign above, “Sprague Aviation School.”  Inside I could make out enough to be sure that it was an aeroplane hangar.

“Hello, Sprague!” called Kennedy, as a man appeared in the light.

The man came closer.  “Why, hello, Kennedy!  What brings you out here at such an hour?”

Craig had jumped from the car, and together the two went into the hangar, while I followed.  They talked in low tones, but as nearly as I could make out Kennedy was hiring a hydro-aeroplane for to-morrow with as much nonchalance as if it had been a taxicab.

As Kennedy and his acquaintance, Sprague, came to terms, my eye fell on a peculiar gun set up in a corner.  It had a tremendous cylinder about the barrel, as though it contained some device to cool it.  It was not a machine-gun of the type I had seen, however, yet cartridges seemed to be fed to it from a disk on which they were arranged radially rather than from a band.  Kennedy had risen to go and looked about at me.

“Oh, a Lewis gun!” he exclaimed, seeing what I was looking at.  “That’s an idea.  Sprague, can you mount that on the plane?”

Sprague nodded.  “That’s what I have it here for,” he returned.  “I’ve been testing it.  Why, do you want it?”

“Indeed I do!  I’ll be out here early in the morning, Sprague.”

“I’ll be ready for you, sir,” promised the aviator.

Speeding back to the city, Kennedy laid out an extensive program for me to follow on the morrow.  Together we arranged an elaborate series of signals, and that night, late as it was, Craig returned to the laboratory, where he continued his studies with the microscope, though what more he expected to discover I did not know.

In spite of his late hours, it was Craig who wakened me in the morning, already prepared to motor out to the aviation school to meet Sprague.  Hastily he rehearsed our signals, which consisted mostly of dots and dashes in the Morse code which Craig was to convey with a flag and I to receive with the aid of a powerful glass.