THE "LIGHTNING CAGE."
"Look at that, will you!" exclaimed Tom.
"What, you are not scared, are you?" asked Jack.
"N-no, but I must say I'm not fond of thunderstorms Particularly when
we are carrying all that gas over our heads."
"That new invention of mine will take care of that all right," said
Jack confidently.
He referred to a new device of his with which the Wondership was
equipped for protecting balloon bags from lightning. In a thunderstorm
a balloon, or gas-filled dirigible, is subject to sudden variations of
electric charge which, under certain conditions, might produce sparks
leading to its annihilation.
More especially was this the case with such a craft as this
Wondership, carrying as she did so much metal and steel wiring. The
netting of the bag, with the idea of making it as conductive as
possible, was of metal, connecting with the other metal parts of the
craft so that when a steel drag rope was lowered to the ground a
discharge of lightning striking the balloon would be passed off
harmlessly into the earth, as is the case with a lightning conductor.
It might be supposed that making the outside of a balloon a good
conductor would invite danger from lightning. But the Boy Inventors
knew that this was not the case. While the ordinary balloon envelope
is a fairly good insulator against low voltage, it is unable to resist
the high tension of atmospheric electricity.
Jack ascertained these facts by touching an electroscope with a bit of
balloon cloth of the kind used on the Wondership, and charged with
2,000 volts of electricity. The electroscope instantly responded.
This showed that the balloon bag increased the electrical tension
immediately above and below it as much as it would do if it was a
perfect conductor, but the destructive action of a lightning bolt
would be greater in proportion to the resistance opposed to it. So
that, in reality, Jack's device was one of the safest that could be
imagined for protecting balloonists in a heavy storm.
In effect, the occupants of the Wondership were enclosed in a cage.
Lightning might zip through the wires and stays, but it could not
touch them. As to the danger of letting out gas through the valve in a
strong electric field, which is almost certain to produce sparks, the
boys did not have to worry about that for to deflate the bag they
simply pumped some of its contents back into the reservoir with the
powerful gas pumps.
But after all, Jack's device had never been tested. It looked as if it
was due to be. The wind came in sharp puffs, now hot and now cold.
Ragged, white clouds, like wind-driven fragments of filmy lace, began
to whip across the dark heavens. The sea turned a peculiar light
green and was flecked with whitecaps.
"We're in for it," said Jack. "Better get up the storm curtains, Tom."
While Jack steered, Tom drew up the waterproof curtains and top which,
in rainy weather, made the Wondership quite dry and weather-tight.
Mica portholes gave light inside this extemporized cabin, and enabled
the steersman to see.
This had hardly been done when a wild gust of wind struck the
Wondership and sent it staggering off its course. But in a jiffy Jack
regained control of the craft and headed her straight for the white
house occupied by Dr. Mays, which could now be seen, its lofty cupola
poking up above the trees surrounding it.
"Glad we're nearly there," said Tom. "I don't much like this."
"We're O.K.," Jack assured him. "We went through a lot worse than this
in that circular storm in Yucatan."
"Can't we drop and run along the road?"
"It's much longer by the road than by the air line, and remember we
are in a big hurry."
"That's so. But we've got the return trip ahead of us."
"Well, if it gets too bad, we'll have to come back by road," said
Jack, "but I haven't got a doubt that she'll stand anything that will
come out of this storm."
Crash!
The sky was rent from end to end by jagged lightning. With a deafening
roar the thunder broke, rumbling and crashing in the sultry air.
S-w-i-s-h!
The rain came in torrents, tearing at the storm curtains. It beat
frantically at them with a noise like that of surf on a beach. But
inside the boys were snug and dry, and the Wondership forged steadily
forward. It was a weird experience for the boys. About them the
artillery of heaven thundered and flashed. They could see each other's
faces and the black outlines of their craft in the livid flare of
flash after flash of lightning.
Jack, with his hands firmly gripping the steering wheel, anticipating
every move of the storm-tossed Wondership like a skillful pilot, felt
his pulses throb. There was something fine in battling with the
elements like this in a stanch craft they had perfected. He felt that
no other airship then in existence would have been able to keep up the
fight.
All at once there came a crash that drove his eardrums in. The
Wondership staggered and then seemed to leap into lambent flame.
Blinded, Jack threw his hands before his eyes, utterly forgetting for
the minute the steering wheel.
Tom gave a shout of alarm, as he felt the craft stagger as if dealt a
mortal blow, and then begin to drop earthward.
"We've been struck!" he yelled in panic.