An accident again changed the current of my ideas. When I was about fifteen years old we had retired to our house near Belrive, when we witnessed a most violent and terrible thunderstorm. It advanced from behind the mountains of Jura, and the thunder burst at once with frightful loudness from various quarters of the heavens. I remained, while the storm lasted, watching its progress with curiosity and delight. As I stood at the door, on a sudden I beheld a stream of fire issue from an old and beautiful oak which stood about twenty yards from our house; and so soon as the dazzling light vanished, the oak had disappeared, and nothing remained but a blasted stump. When we visited it the next morning, we found the tree shattered in a singular manner. It was not splintered by the shock, but entirely reduced to thin ribbons of wood. I never beheld anything so utterly destroyed.

What would have to change for there to be dialogue in this passage?

Fewer characters would have to appear.
The passage would have to be shorter.
More characters would have to appear.
The passage would have to be scarier.

In literature, a dialogue takes place when two or more characters interact and share ideas, because of this, a dialogue is only possible if there are at least two characters that speak between them. In the case of the passage presented, there is only one character who is also the narrator and tells the reader about a particular experience he had when he was fifteen years old. Additionally, during this passage, the only character is the narrator as other characters are not mentioned.

Considering this, to include dialogue in this passage or change all the content into a dialogue it is necessary to include more characters, as only if there are more characters involved there can be a conversation and interaction between them and this can serve to tell the events using dialogue. Therefore, the aspect that needs to be changed is that more characters would have to appear.