How does Lee use humor to change the tone of Atticus's conversation with the children about the jury verdict?To Kill a Mockingbird by Harper Lee

In Chapter 22 of Harper Lee's To Kill a
Mockingbird, Jem asks his father how it has been possible that with the
evidence before them a jury could bring in a verdict of guilty against Tom Robinson.  It
is a somber and discouraged Atticus Finch who answers, "I don't know, but they did
it...seems that only children weep."  After this, he says "Good night" and goes to bed. 
Scout narrates that things are always better in the morning, and
Atticus, nevertheless, "rose at his usual ungodly
hour."

Anotherhumorous remark occurs after
Calpurnia shows Atticus all the gifts of food that the black community has brought
Atticus in appreciation of his sincere and thorough defence of
Tom:

....The
kitchen table was loaded with enough food to bury the family....Atticus
grinned when he found a jar of pickled pigs' knuckles.  "Reckon Aunty'll let me eat
these in
the diningroom?"

By
means of two of Scout's descriptions, and by Atticus's tongue-in-cheek remark about his
sister's "persnickety" personality, Harper Lee injects humor into a melancholic
situation.