their greatest desires was to help the professor turn out a craft
even more wonderful than the Electric Monarch, the Porpoise or
the Flying Mermaid. It was in this connection that Jack was
experimenting on the new gas, when the slight accident happened.

"Are you going to try that again?" asked Mark, as he and his chum
walked along to their geometry class.

"Sure," replied Jack. "I want that to succeed. I know I am on
the right track."

"You came near getting blown off the track," remarked his
companion, which was as near to a joke as he ever would come,
for, though Jack was jolly and full of fun, Mark was more
serious, inclined to take a sterner view of life.

"Oh, I'll succeed yet!" exclaimed Jack. "And when I do--you'll
see something--that's all."

"And feel it, too," added Mark, putting his hand on his head, the
book having raised quite a lump.

It was several days after this before the boys had the chance to
work alone in the laboratory again, and Jack had to promise not
to try his experiment with the new gas before this privilege was
granted him.

"Want any help?" asked Dick Jenfer, another student, as he saw
Jack and Mark enter the laboratory.