and then I'm
going to make new plates."

Tom made some memoranda, and then, giving Koku the order for the
chemist, the young inventor closed up his shop, and went with Ned
down to Lake Carlopa, where the motor boat was moored.

This was not the same boat Tom had first purchased, some years
ago, but a comparatively new and powerful craft.

"It sure is one grand little day for a ride," remarked Ned, as he
got in the craft, while Tom looked over the engine.

"Yes, I'm glad you came over, and routed me out," said the young
inventor. "When I get going on a thing I don't know enough to
stop. Oh, I forgot something!"

"What?" asked Ned.

"I forgot to leave word about Mr. Railing's airship. It's all
fixed and ready for him, but I put on a new control, and I wanted
to explain to him about it. He might not know how to work it. I
left word with father, though, that if he came for it he must not
try it until he had seen me. I guess it will be all right. I don't
want to go back to the house now."

"No, it's too far," agreed Ned.

"I have it!" exclaimed Tom. "I'll telephone to dad from here, not
to let Halling go up until I come back. He may not come for his
machine; but, if he does, it's best to be on the safe side Ned."

"Oh, sure."

Accordingly, Tom 'phoned from his boat-house, and Mr. Swift
promised to see the bird-man if he called. Then Ned and Tom gave
themselves up to the delights of a trip on the water.

The Kilo, which name Tom had selected for his new craft, was a
powerful boat, and comfortable. It swept on down the lake, and
many other persons, in their pleasure craft, turned to look at
Tom's fine one.

"Lots of folks out to-day," observed Ned, as they went around a
point of the shore.

"Yes, quite a number," agreed Tom, leaning forward to adjust the
motor. "I wonder what's got into her?" he said, in some annoyance,
as he made various adjustments. "One of the cylinders is missing."

"Maybe it needs a new spark plug," suggested Ned.

"Maybe. Guess I'll stop and put one in."

Tom slowed down the motor, and headed his boat over toward shore,
intending to tie up there for a while.

As he shifted the wheel he heard a cry behind him, and at the same
time a hoarse, domineering voice called out:

"Here, what do you mean, changing your course that way? Look out,
or I'll run you down! Get out of my way, you land-lubber, you!"

Startled, Ned and Tom turned. They saw, rushing up on them from
astern, a power