Lance, "how do the torpedoes fly? What motivates them?"

"A closely guarded secret, of course," he was told. "I merely possess
a slight comprehension of it. I know that it is an adaptation of that
discovery of Professor Singe, two years ago--cosmic attraction.
Eventually, perhaps, it will permit interplanetary travel. This use of
it is simply the beginning. But it is to America's everlasting glory
that a scientist of hers developed it.

"You know how a sliver of wood is propelled by the ripples of a pond?
Vibrations of the water, really. Well, evidently there are somewhat
similar vibrations in the ether, cosmic force. Each one of these
flying torpedoes contains a highly expensive, intricate mechanism
which transforms this invisible vibration-power into material
propulsion. The mechanism is adjusted to propel the torpedo at such an
altitude in such a direction. We possess no means of setting the
machines to _stop_ at a certain place and so tumble earthwards. That's
where you and Hay come in.

"Hay is now, with forged documents, passing himself off as a regular
Slav pilot. He speaks the tongue. Two nights from now, you, Lance,
keep a rendezvous with Hay at an isolated ranch in the Lake Tahoe
country--the Sola Ranch, where we staged that big fight a few months
back."

* * * * *

Lance nodded.

"In your plane is an instrument which is the kernel of the scheme. It
arrives here to-morrow. It's a device which shoots an invisible beam
fifty miles into the air, a negative beam, in sympathy with the
machinery on the torpedoes. Hay sets this device near the Slav
headquarters. The torpedo squadron takes off from a few hundred miles
behind here, flying in the direction of the heart of the Slav forces.
When they run into the beam, their motive power is nullified, and down
they fall. Crash! The Slavs are wiped out. Our troops charge forward
in a grand attack; the Slavs, with no armament, no reinforcing troops,
no supply of tanks and flame throwers, crumple. The invasion of
America is put to an end!"

Lance rose. His face was alight, his eyes burning with strong,
unquenchable fire.

"It's great, sir, great! It can't fail! By God, if it takes every last
drop of my blood, I'll help Hay put this through!"

Colonel Douglas extended his right hand and Lance's met it in a firm
shake. In the thick silence they stood thus for some minutes. Then,
without moving so much as a cheek muscle, the colonel wh