“Go on back, unless you want to be shot!” cried the man savagely, but they paid no attention to the threat as no pistol appeared; and, seeing this, the thief redoubled his efforts to get away.

He was still a quarter of the distance from the opposite shore, and the boys on the tree were in midstream, when Sam uttered a shout.  “There goes one of his oars!  We can catch him now —­ if we try hard!”

It was true that the oar was gone, and in his anxiety to regain the blade the tramp nearly lost the second oar.  But his efforts were unavailing, and he started to paddle himself to the bank, meanwhile watching his pursuers anxiously.

“We’ll get him,” said Dick encouragingly, when, splash!  Tom went overboard like a flash, the lower end of his pole having slipped on a smooth rock of the river bottom.  There was a grand splutter, and it was fully a minute before Tom reappeared —­ twenty feet away and minus his pole.

“Hi! help me on board, somebody!” he spluttered, for he had gone overboard so quickly that he had swallowed a large quantity of water.

Both Sam and Dick tried to reach him, but could not.  Then the current caught the tree and whirled it around and around until both boys began to grow dizzy.

Seeing they could not aid him, and getting back a little of his wind, Tom struck out for the tree.  But the water running over his face blinded him, and ere he knew he was so close the tree came circling around and struck him on the side of the head.

“Oh!” he moaned, and sank from sight.

“Tom’s hit!” gasped Sam.  “He’ll be drowned sure now!”

“Not if I can help him!” burst out Dick, and leaped overboard to his brother’s assistance.  But Tom was still out of sight, and for several seconds could not be located.

Sam waited anxiously, half of a mind to jump into the river himself.  The tramp was now forgotten, and landed on the opposite bank unnoticed.  He immediately dove into the bushes, and disappeared from view.

At last Dick caught sight of Tom’s arm and made a clutch for it.  Hardly had he taken hold than Tom swung around and caught him by the throat in a deathlike grip, for he was too bewildered to know what he was doing.

“Save me!” he groaned.  “Oh, my head!  Save me!”

“I will, Tom; only don’t hold me so tight,” answered Dick.  “I —­ can’t get any air.”

“I can’t swim —­ I’m all upset,” was the reply; and Tom clutched his elder brother tighter than ever.

Seeing there was no help for it, Dick caught hold of the fingers around his throat and forced them loose by main force.  Then he swung himself behind Tom and caught him under the arms, in the meantime treading water to keep both of them afloat.

“Sam, can’t you bring that tree closer?” he called out.

There was no reply, and, looking around, he saw that the tree and his younger brother were a hundred yards away, and sailing down the river as rapidly as the increasing current could, carry them for quarter of a mile below were what were known as the Humpback Falls —­ a series of dangerous rapids through which but few boats had ever passed without serious mishap.