In to kill a mocking bird what was the offering for at church?

In To Kill a Mockingbird, the offering at church is money. This is specifically mentioned when Scout and Jem are at the First Purchase church service with Calpurnia:

> "Jem, Calpurnia said, 'Do you have any money to put in the collection plate?'

>

> 'No,' Jem whispered.

>

> 'Don't worry,' Calpurnia said. 'You don't have to. I put enough in for the both of you.'"

The offering is collected to support the church and its various activities.