What are the digressions in Henry Fielding's novel Tom Jones?

There are several instances of digressions in Tom
Jones.

One example of them is the introduction of each
chapter. Fielding gives us a hint of what the reader is to expect in the chapter that he
or she is about to read.

Another- In the first 2 chapters
of the story, we learn about the background of Mr. AllWorthy, the loss of his family,
how he came about his wealth, his position in society, and much more about his sister et
al.  This, while not directly a part of Tom Jones's own story, is a sermon that Fielding
explains is necessary for the reader to know before
hand.

Another example (a very good one) was the sermon that
Dielding gave Jenni Jones, Tom's mother, on how her decision to get involved in a
relationship, have a child out of wedlock, and then abandoning the child, broke with
every canon of morality and social behavior, and that she should be shun from society as
a misfit and as an immoral person.

This is a good example
because the preaching that Allworthy gives to Jones is almost a complete story of its
own. It has a beginning, middle, and end, hints to causes and effects, cites on a
diversity of matters, and could be read independently from the rest of the story, still
making complete sense to the reader.

These forms of long,
often a bit wearisome, and highly moral moments in storytelling are often separated from
the main topic of the story, but are meant to make a point related to it. In this case,
it was the sad way in which Tom Jones was found, and the origins of his being with the
Allworthys.