In chapter 10 of The Hobbit, what does Bilbo learn by eavesdropping on the conversation of the raftsmen?
When he overhears the raftmen talking, Bilbo learns that it is harder to get to The Lonely Mountain than they thought.
By this point, Bilbo is tired and a bit grumpy. He has been through a lot. He is also finally in sight of The Lonely Mountain, and getting closer seems to bring only more peril.
The Lonely Mountain! Bilbo had come far and through many adventures to see it, and now he did not like the look of it in the least. (ch 10)
Bilbo learns that there are problems in getting to The Lonely Mountain that he and his friends did not know about. For one thing, “the roads out of the East towards Mirkwood vanished or fell into disuse.” Not only that, even the banks of the river are treacherous because the Lake-men and the Wood-elves can’t agree on whose responsibility it is to take care of them.
Things have changed since the dwarves where last there. There was flooding and “an earthquake or two” attributed to the dragon. The path had vanished, and “marshes and bogs had spread wider.” People have ventured in that direction and never returned. Bilbo is not encouraged.
Bilbo's instincts about the mountain seem to be accurate. Now that they are about half-way through the journey, they can see that things are not getting any easier.