practically rebuilt the Advance."

"Yes; and I think she's a much better craft, too, Father."

"Glad to hear that, Tom. Of course you kept the gyroscope
rudder feature?"

"No, I didn't," replied Tom. "If I had left that installed it
would have meant carrying a smaller diving bell, and I think that
last will be more useful than the gyroscope. I put in a set of
double-acting depth rudders instead."

Mr. Swift shook his head.

"I'm sorry for that, Tom," he remarked. "There's nothing like
the gyroscope rudder in a tight pinch--say when there's a storm.
And for holding the boat steady, if you have to make a sudden
turn under water, to avoid an obstruction you come upon
unexpectedly, a gyroscope can't be improved on. It holds you
steady and prevents your turning turtle."

"I've put side fin-keels to correct that," Tom explained.

But still his father was not satisfied.

"I'd rather you had kept the gyroscope," he said, and the time
was to come when Tom Swift wished that himself.

But it was too late to make the change now, and so, with more
than usual confidence in his own designing abilities, the next