What details in Part III suggest that Farquhar's journey occurs in his mind?
Everything seems to fall perfectly into place during the final chapter of Ambrose Bierce's short story, "An Occurrence at Owl Creek Bridge." However, all of the events seem too easy--too contrived. The pain in his neck would be normal had the rope actually broken, but it is a hint to the actual outcome. His oscillating body, like a swinging "pendulum," is another clue to his true fate. The light became "fainter and fainter until it was a mere glimmer." The swirling water that threw him out of the range of the guns is far too coincidental, and the music similar to that of "Aeolian harps" is another clue from Bierce that relates to his death. Perhaps the most obvious example is that of his journey homeward; he makes the long trek back to his plantation in just a matter of hours, though it must have been many miles in reality.
To me, there are a few major things that suggest that this journey is not truly taking place.
First, he seems too aware for it to be real. He is, for example, able to see the bullets that have hit the water and are drifting down towards where he is. That seems unrealistic.
Second, his consciousness seems sort of weird. He sees his own hands as separate from himself. He sees this vortex of color where everything (trees, sky, etc) is indistinct.
Finally, the soldiers' actions seem unlikely. This is especially true of the cannon. It seems so unlikely that they would fire a cannonball (not very accurate) at him. And then it seems unlikely that they would miss if they used grapeshot.