I have spent most of the day putting in a comma and the rest of the day taking it out.
As a blogger who blogs about writing, I try my damnedest to stay away from referring to grammar geek favorites like attributive adjective, future perfect progressive, and reflexive pronoun on the theory that once you’ve graduated eighth grade, references to terminology like this can cause a person to lose all interest in becoming a better writer. So it pains me to have to refer to a compound predicate, but refer I must because it's the cause of one of the most common errors I see.
A compound predicate occurs when two or more verbs share the same subject. Usually they’re connected with the word “and.” In such a case, the phrases, the two predicates, are not divided by a comma.
While it’s true that you might pause for a sec after the word that comes before “and” (in this case, “galleries”), that doesn’t mean it requires what Washington Post grammar guru Bill Walsh calls a "take a breath" comma. Both the verbs, “ambled” and “scrutinized,” refer to Silas, so no comma needs to divide them.
Even sentences like this that are much more complicated don’t take a comma:
No doubt you took an eencie-beencie teeny-tiny breath between "Piemonte" and “and,” and I’m glad you did, since, as my grandmother Dora would have said, I want you should be happy. But what you don’t need to do is add a comma there. Jose is the subject and “clapped” and “joined” are the verbs.
Watch out for this common sentence construction and help prevent me from ever again having to use the phrase compound predicate!