Thus the track line was broken for a couple of feet or so by this obstacle.
Supposing that the creature which had passed here had clambered over the log, Tom's scouting instinct was aroused to examine the rough bark carefully for any little tuft of hair which the animal might have left.
And not finding any, he was puzzled.

For by its tracks the creature must have been very small, certainly too small to have stepped, and not at all likely to have jumped over the log.

If then it had clambered over the log it seemed remarkable that it had left no trace, not even a single hair, upon that rough surface.
Tom knew that this was unusual.

He knew that old Uncle Jeb would laugh at him if he went back and said that some small creature had crawled over that nutmeg grater and left no sign of its crossing.

He knew that no animal could graze a tree in its flight but old Uncle Jeb would find there some tell-tale souvenir of its passing.
Tom's interest was keenly aroused now.