, Ned Newton and I will cruise about and we'll take you along any
time you want to go. We're going to camp out nights or sleep in the
boat if it rains. I've ordered a canopy with side curtains. Ned and I
don't care for the hotel life in the summer. Will you go?"

Mr. Swift considered a moment. He did need a rest, for he had been
working hard and his brain was weary with thinking of many problems.
His son's program sounded very attractive.

"I think I will accept," said the inventor with a smile. "When can you
start, Tom?"

"In about four days. Ned Newton, will get his vacation then and I'll
have the canopy on. I'll start to work at it to-morrow. Then we'll go
on a trip."

Sandport was a summer resort at the extreme southern end of Lake
Carlopa, and Mr. Swift at once wrote to the Lakeview Hotel there to
engage a room for himself. In the meanwhile Tom began to put the
canopy on his boat and arrange for the trip, which would take nearly a
whole day. Ned Newton was delighted with the prospect of a camping
tour and helped Tom to get ready. They took a small tent and plenty of
supplies, with some food. They did not need to carry many rations, as
the shores of the lake were lined with towns and villages where food
could be procured.

Finally all was ready for the trip and the night before the start Ned
Newton stayed at Tom's house so as to be in readiness for going off
early in the morning. The day was all that could be desired, Tom
noted, as he and his chum hurried down to the dock before breakfast to
put their blankets in the boat. As the young inventor entered the
craft he uttered an exclamation.

"What's the matter?" asked Ned.

"I was sure I locked the sliding door of that forward compartment," was
the reply. "Now it's open." He looked inside the space occupied by
the gasoline tank and cried out: "One of the braces is gone! There's
been some one at my boat in the night and they tried to damage her."

"Much harm done?" asked Ned anxiously.

"No, none at all, to speak of," replied Tom. "I can easily put a new
block under the tank. In fact, I don't really need all I have. But
why should any one take one out, and who did it? That's what I want to
know."

The two lads looked carefully about the dock and boat for a sign of the
missing block or any clews that might show who had been tampering with
the ARROW, but they could find nothing.

"Maybe the block fell out," suggested Ned.

"It could