was slightly out of order. There
would be no time to stop and repair it then.

Luckily the Wondership still stood outside the shed. Five minutes
later the boys were soaring aloft, bound for the doctor's house, which
was some distance away. It was not till they had fairly started that
they noticed the change in the weather.

The thunderheads they had seen earlier in the day now spread and
covered the whole sky with a dark pall. The air was very still, as if
nature was holding her breath. Far off, though in plain view, the sea
was lying like a smooth sheet of steel-gray velvet. A sailing ship,
with sails flapping, was becalmed some distance from shore.

"Going to rain," said Tom.

"Worse than that, I think," said Jack. "We're in for the storm that's
been making up for two days now."

"Well, we can get there and back before it breaks."

"Easily. Let those motors out, Tom, we want to make good time."

It was oppressively hot, and had it not been for Jack's anxiety he
would have enjoyed the swift cooling passage through the thundery air.
But he was strangely troubled. Did that letter mean that his father
was on the verge of ruin?

Suddenly he bethought himself of Ned Nevins' letter. He opened it,
having pushed it into his pocket when they entered the workshop, where
Mr. Chadwick had placed it before opening the ominous epistle from his
brokers. It was a friendly, chatty note from the boy, and enclosed the
checks covering the joint dividends of Jack and Tom in the
Hydroaeroplane Company.

"Well, at any rate, that's something," declared Jack to Tom, as he
handed him the letter and his check.

"Yes, but if Uncle Chester is ruined, it's only a drop in the bucket,"
said Tom.

"Well, it's no use crossing your bridges till you come to them," said
Jack, "and anyhow, that letter may be only a false alarm. I've heard
they get these financial panics in Wall Street just like kids get the
measles, and they get over them as quickly."

"I trust it will be so in this case," said Tom.

"So do I," said Jack hopefully, but a cold fear that his father was
ruined possessed him, and made his heart feel heavy as lead.

Suddenly, from the purple firmament, came the sound of distant
thunder. Following it a puff of wind, hot as the exhalation of an
opened oven, blew in their faces. In the distance they saw a ragged
streak of lightning tear the cloud curtains.

CHAPTER XIX.

THE "LIGHTNING CAGE."

"Look at that, will yo