What Verne might be saying about Harry if he has been "defeated" by the professor's scientific arguments is that Harry is not very intellectual
Explanation:
The expression defeated it is normally used in terms of fights or matches, any kind of competition as a general rule, the winner is the one that defeats, therefore The professor who was the winner had more knowledge and more concise arguments that Harry which demonstrates that he doesn't have as much intellectual knowledge as the professor does.
The major theme of The Dream of the Rood, is the representation of the crucifixion as a battle. Both Christ and the Cross triumph over defeat, they are seen as heroic. In the end, they are both worshiped because of what they signify.
The bird is generally thought to symbolism freedom, they can walk on the earth and swim in the sea as humans do but they also have the ability to soar into the sky. Birds are free to roam to earth and the sky. Many cultures believe that they symbolise eternal life; the link between heaven and earth.
