the cogs, and
getting rid of the off-set shaft, also by increasing the number of
revolutions, and perhaps by using a new style of carburetor, we can
get more speed and power."

"Then we'll do it!" cried Mr. Fenwick, with enthusiasm. "I knew I
hadn't got everything just right. Do you think it will work after
that?"

"Well," remarked Tom, hesitatingly, "I think the arrangement of the
planes will also have to be changed. It will take quite some work,
but perhaps, after a bit, we can get the WHIZZER up in the air."

"Can you begin work at once?" asked the inventor, eagerly.

Tom shook his head.

"I can't stay long enough on this trip," he said. "I promised father
I would be back by to-morrow at the latest, but I will come over
here again, and arrange to stay until I have done all I can. I need
to get some of my special tools, and then, too, you will require
some other supplies, of which I will give you a list. I hope you
don't mind me speaking in this way, Mr. Fenwick, as though I knew
more about it than you do," added Tom, modestly.

"Not a bit of it!" cried the inventor heartily. "I want the benefit
of your advice and experience, and I'll do just as you say. I hope
you can come back soon."

"I'll return the first of the week," promised Tom, "and then we'll
see what can be done. Now I'll go over the whole ship once more, and
see what I need. I also want to test the lifting capacity of your
gas bag."

The rest of the day was a busy one for our hero. With the aid of Mr.
Damon and the owner of the WHIZZER, he went over every point
carefully. Then, as it was too late to attempt the return flight to
Shopton, he telegraphed his father, and he and Mr. Damon remained
over night with Mr. Fenwick.

In the morning, having written out a list of the things that would
be needed, Tom went out to Franklin Field, and repaired his own
monoplane. It was found that one of the electric wires connected
with the motor had broken, thus cutting off the spark. It was soon
repaired, and, in the presence of a large crowd, Tom and Mr. Damon
started on their return flight.

"Do you think you can make the WHIZZER work, Tom?" asked Mr. Damon,
as they were flying high over Philadelphia.

"I'm a little dubious about it," was the reply. "But after I make some
changes I may have a different opinion. The whole affair is too big
and clumsy, that's the trouble; though the electrical part of it is
very good."

Shopton was reached without incide