Why does Miss Maudie make a comparison between a "Roman carnival" and the people passing by to attend the trial at the courthouse in Harper Lee's To Kill a Mockingbird?
In Chapter 16 of Harper Lee's To Kill a Mockingbird, Jem, Dill, and Scout stand outside observing all of the county's folks journeying to the courthouse in town on the day of Tom Robinson's trial. Miss Maudie also comes out on her porch just as a wagonload of foot-washers drive past, mocking Miss Maudie for the vanity she displays in her yard full of summer flowers. After Miss Maudie mocks them right back, the kids approach her house to converse with her. When the kids ask her if she is going to the courthouse to observe the trial, Miss Maudie replies:
I am not. 't's morbid, watching a poor devil on trial for his life. Look at all those folks, it's like a Roman carnival. (Ch. 16)
By speaking of a "Roman carnival," Miss Maudie is referring to the fact that Roman Catholics have a time of festival just before their period of Lent. The festival, generally called Carnival or even Mardi Gras in some places, is a time of wild entertainment marked by parades, theater, singing, and folk dancing. Attendees also wear costumes. The Carnival season is in general considered a wild time in which attendees abstain from the restrained, moral behavior the Catholic religion usually requires. It is especially a time to cut loose just before the season of Lent, a 40-day period in which members of the Roman Catholic Church fast, don't eat meat, and abstain from other worldly pleasures in order to imitate Jesus Christ's own 40-day period of fasting in the desert.
The Carnival season begins at different times in different places around the world dominated by the Roman Catholic Church. For example, in Bavaria, Carnival lasts more than a month and begins as early as the feast of the Epiphany, which takes place on January 6th, and lasts until the Tuesday just before Ash Wednesday, called Shrove Tuesday. In Cologne, Carnival begins even earlier, on November 11th, making it a nearly 3-month-long celebration. However, other areas are stricter. For example, in France, Carnival is only celebrated on Shrove Tuesday.
Hence, in referring to the town as looking like a Roman carnival and attendees of the trial as Carnival attendees, Miss Maudie is commenting on the fact the citizens look like they are going out for a time of wild merry-making, a time when all morality is forgotten for a period. Since many of the county's citizens, including the members of the jury, believe Robinson to be guilty simply because they are racist, we know that Miss Maudie's simile comparing the citizens to Carnival attendees is very fitting.