Two of the thieves were at the oars, and, with one accord, they at once increased their speed.  The boat swung about sharply and was headed for the shore, which they seemed to have come from only a short time previous, as the craft was not far out in the lake.

“No, you don’t!” cried Tom.  “I see your game!  You want to get to the woods, where you’ll have a better chance to escape!  If this isn’t great luck, coming upon them this way!”

It was the work of but a moment to speed up the engine and head the arrow for the rowboat.  The men were pulling frantically, but they had no chance.

“Get between them and the shore!” cried Mr. Sharp.  “You can head them off then.”  This was good advice and Tom followed it.  The men, among whom the lad could recognize Happy Harry and Anson Morse, were all excited.  Two of them stood up, as though to jump overboard, but their companions called to them to stop.

“If we only had a gun now, not to shoot at them but to intimidate them,” murmured the balloonist, “maybe they’d stop.”

“Here’s one,” answered Tom, pointing to the seat locker, where he kept the shotgun Mr. Duncan had given him.  In a moment Mr. Sharp had it out.

“Surrender!” he cried, pointing the weapon at the men in the small boat.

“Don’t shoot!  Don’t fire on us!  We’ll give up!” cried Happy Harry, and the two with the oars ceased pulling.

“Don’t take any chances,” urged Mr. Sharp in a low voice.  “Keep between them and the shore.  I’ll cover them.”  Tom was steering from an auxiliary side wheel near the motor, and soon the arrow had cut off the retreat of the men.  They could not land and to row across the lake meant speedy capture.

“Well, what do you want of us?” growled Morse.  “What right have you got to interfere with us in this fashion?”

“The best of right,” answered Tom.  “You’ll find out when you’re landed in jail.”

“You can’t arrest us,” sneered Happy Harry.  “You’re not an officer and you haven’t any warrant.”

Tom hadn’t thought of that, and his chagrin showed in his face.  Happy Harry was quick to see it.

“You’d better let us go,” he threatened “We can have you arrested for bothering us.  You haven’t any right to stop us, Tom Swift.”

“Maybe he hasn’t, but I have!” exclaimed John Sharp suddenly.

“You!  Who are you?” demanded Featherton, alias Simpson, the man who had run the automobile that carried Tom away.

“Me.  I’m a special deputy sheriff for this county,” answered the balloonist simply.  “Here’s my badge,” and, throwing back his coat, he displayed it.  “You see I got the appointment in order to have some authority in the crowds that gather to watch me go up,” he explained to Tom, who plainly showed his astonishment.  “I found it very useful to be able to threaten arrest, but in this case I’ll do more than threaten.  You are my prisoners,” he went on to the men in the boat, and he handled the shotgun as if he knew how to use it.  “I’ll take you into custody on complaint of Mr. Swift for robbery.  Now will you go quietly or are you going to make a fuss?” and Mr. Sharp shut his jaw grimly.