d that was now given up pretty much to thistles
and burdocks, with a sprinkling of iron-weeds.

It was rather rough sledding, to be sure, and as the bicycle wheels
pounded over the turf the boys had to hold on to keep their seats.

But when sufficient momentum had been acquired, Frank elevated the fore
plane, and immediately there was the greatest relief felt; for they
began to rise in the air, and all that terrible bumping stopped for
good. The change was wonderful, and it felt as though they were gliding
on velvet.

"We're off!" exclaimed Andy, exultantly.

Frank said nothing. He did not possess quite the same sanguine nature
that his cousin had. Andy seldom allowed thoughts of possible disaster
to annoy him, but on the other hand Frank was always trying to head off
trouble.

He realized that with this launching of their new hydro-aeroplane they
would be entering upon an extra hazardous game, the outcome of which no
one could foresee. The two men whom they expected to follow must be
desperate fellows, who would resort to almost any hazard rather than
allow themselves to be caught.

And it was not an amateur aviator like Percy Carberry who was opposed
to them now, but one who had had long experience in the art of
harnessing a flying machine to do his bidding.

Once they left the ground behind them, Frank started to spiral upward
much in the same way the others had done. One thing he was glad of, and
this was the presence of Andy alongside. Casper Blue might be a daring
air pilot, but with his companion a perfect greenhorn in all that
pertained to the art, he would be more or less handicapped. A sudden
incautious movement on the part of the novice might prove the undoing of
the precious pair.

Once they had risen to a certain height, and the aeroplane was turned so
as to follow the other air craft, which was speeding away, headed
directly into the north. Of course, those aboard must know that they
were being chased. They could not have failed to see the hydroplane, (as
it is generally called, though the true word to cover it would be
hydro-aeroplane) even before it left the field, once they started to
ascend.

"Well, we're off at last!" commented Andy, in a satisfied tone, when the
course had been taken, and they were following directly after the
fugitive air craft.

"And let's hope we'll come out of this adventure as luckily as we have
on other occasions," remarked sober Frank.

"Wonder if Perc happens t