Tom took hold of the handle, which Eradicate gladly relinquished to him, and his trained touch told him at once what was the trouble.

“Some one has had the wheels off and put them on wrong, Rad,” he said.  “The ratchet and pawl are reversed.  This mower would work backwards, if that were possible.”

“Am dat so, Mistah Swift?”

“That’s it.  All I have to do is to take off the wheels and reverse the pawl.”

“I—­I didn’t know mah lawn-moah was named Paul,” said the colored man.  “Is it writ on it anywhere?”

“No, it’s not the kind of Paul you mean,” said Tom with a laugh.  “It’s spelled differently.  A pawl is a sort of catch that fits into a ratchet wheel and pushes it around, or it may be used as a catch to prevent the backward motion of a windlass or the wheel on a derrick.  I’ll have it fixed in a jiffy for you.”

Tom worked rapidly.  With a monkey-wrench he removed the two big wheels of the lawn-mower and reversed the pawl in the cogs.  In five minutes he had replaced the wheels, and the machine, except for needed sharpening, did good work.

“There you are, Rad!” exclaimed Tom at length.

“Yo’ suah am a wonder at inventin’!” cried the colored man gratefully.  “I’ll cut yo’ grass all summah fo’ yo’ to pay fo’ this, Mistah Swift.”

“Oh, that’s too much.  I didn’t do a great deal, Rad.”

“Well, yo’ saved me from bein’ swindled, Mistah Swift, an’ I suah does ’preciate dat.”

“How about the fellow you traded the cracked grindstone to, Rad?”

“Oh, well, ef he done run it slow it won’t fly apart, an’ he’ll do dat, anyhow, fo’ he suah am a lazy coon.  I guess we am about even there, Mistah Swift.”

“All right,” spoke Tom with a laugh.  “Sharpen it up, Rad, and start in to cut grass.  It will soon be summer,” and Tom, leaping upon his motor-cycle, was off like a shot.

He found his father in his library, reading a book on scientific matters.  Mr. Swift looked up in surprise at seeing his son.

“What!  Back so soon?” he asked.  “You did make a flying trip.  Did you give the model and papers to Mr. Crawford?”

“No, dad, I was robbed yesterday.  Those scoundrels got ahead of us, after all.  They have your model.  I tried to telephone to you, but the wires were down, or something.”

“What!” cried Mr. Swift.  “Oh, Tom!  That’s too bad!  I will lose ten thousand dollars if I can’t get that model and those papers back!” and with a despairing gesture Mr. Swift rose and began to pace the floor.

CHAPTER XVIII.

HAPPY HARRY AGAIN

Tom watched his father anxiously.  The young inventor knew the loss had been a heavy one, and he blamed himself for not having been more careful.

“Tell me all about it, Tom,” said Mr. Swift at length.  “Are you sure the model and papers are gone?  How did it happen?”