panion and his
thick, bull-like neck.

"No, thanks," he said. "I've got to be getting back. There's another type
of machine I've got to look over out at Mineola. It is really necessary
that I reach there as quickly as possible."

"Very well," said Mortlake, inwardly relieved, as he didn't much fancy
duplicating Roy's feat, "we'll head straight on for the shore."

"If you please."

But what was the _Golden Butterfly_ doing? As the steamer raced onward,
that aerial wonder had swung in a spiral, and was now seemingly hovering
about, awaiting the arrival of the _Silver Cobweb_.

As the two aeroplanes drew abreast, Mortlake muttered something, and bent
over his engines. The _Cobweb_ leaped forward like an unleashed greyhound.
But the _Golden Butterfly_ was close on her heels, and making almost as
good time. Mortlake plunged his hands in among the machinery and
readjusted the air valve of the carburetor. Another increase of speed
resulted. The indicator crawled up to sixty-six, sixty-eight and then to
seventy miles an hour.

"Pressing her a bit, aren't you?" asked the officer, as they seemed to
hurtle through the air, so fast did they rush onward.

"Oh, no. She's built for speed," responded Mortlake, with a gratified
grin; "she'll leave any such old lumber wagon as that Prescott machine
miles behind her any day in the week."

This seemed to be true. The _Golden Butterfly_, making about sixty miles,
was being rapidly left behind.

"I should think you'd be afraid of overheating your cylinders,"
volunteered the lieutenant.

Now, this was just what Mortlake was afraid of. But, as has been said, he
was the sort of man who, in sporting parlance, was willing always "to take
a chance" to beat any one he considered his rival. He was taking a
desperate chance now. Under the artificial means he had used to increase
the speed of his engines, the motor was "turning up" several hundred more
revolutions a minute than she had been built for.

Now they shot above the strip of white beach, and, below them the pleasant
meadow-lands and patches of verdant woods began to show once more.

All at once, the sign for which Mortlake had been watching so anxiously
manifested itself. A tiny curl of smoke ascended from one of the
cylinder-heads. A smell of blistering, burning paint was wafted back to
the nostrils of Lieut. Bradbury.

"I thought so," he said; "overheating already. Better slow down,
Mortlake."

Mortlake glanced back. The