Finley says that the camp meeting is like the roar of niagara. what is the comparing?

For Finley to say that the camp meeting is like the roar of Niagara Falls is to draw a simile to two different variables. Since roaring is making a large noise, the Niagara Falls makes a very large sound as it is a very large waterfall. So Finley is stating that for the camp meeting to roar like Niagara Falls, it is a very loud and active meeting.