he storage-battery room? His eyes
followed the wires along the wall. Yes, they ran to the terminals of the
battery. It dawned upon him that there might be something here undreamed
of in electrical engineering--a storage battery for an alternating
current!

The electrician closed a row of switches, brought the two polished brass
spheres of the discharger within striking distance, and instantly a
blinding current of sparks roared between the terminals. He had been
right. This battery not only was charged by an alternating current, but
delivered one of high potential. He peered into the cells, racking his
brain for an explanation.

"Atterbury," said he meditatively, "did I ever tell you why they do
that?"

"Yes," answered the man. "You--told me--once. The two metals--in the
electrolyte--come down--on the plates--in alternate films--as--the
current changes direction. But you never told me--what the electrolyte
was--I don't suppose--you--would be willing to now, would you?"

"H'm," said Bennie, "some time, maybe."

But this cue was all that he required. A clever scheme! Pax had formed
layers of molecular thickness of two different metals in alternation by
the to-and-fro swing of his charging current. When the battery
discharged the metals went into solution, each plate becoming
alternately positive and negative. He wondered what Pax had used for an
electrolyte that enabled him to get a metallic deposit at each
electrode. And he wondered also why the metals did not alloy. But it
would not do for him to linger too long over a mere detail of equipment.
And he turned away to continue his tour of inspection, a tour which
occupied most of the morning, and during which he found a well-stocked
gallery and made himself a cup of coffee.[5]

[Footnote 5: He even climbed with Atterbury to the very summit of the
tractor, where he discovered that his original guess had been correct
and that the car rose from the earth rocket fashion, due to the back
pressure of the radiant discharge from a massive cylinder of uranium
contained in the tractor. Against this block played a disintegrating ray
from a small thermic inductor, the inner construction of which he was
not able to determine, although it was obviously different from his own,
and the coils were wound in a curious manner which he did not
understand. There might be something in Hiroshito's theory after all.
The cylinder of the tractor pointed directly downward so that the blast
w