Punctuation / A Primer of Information about the Marks of Punctuation and their Use Both Grammatically and Typographically

by Frederick W. Hamilton

If the copy is hard to read, the compositor will set but few pages.

15. To separate introductory words and phrases and independent adverbs from the rest of the sentence.

Now, what are you going to do there?

I think, also, Franklin owed much of his success to his strong common sense.

This idea, however, had already been grasped by others.

Of course the comma is not used when these adverbs are used in the ordinary way.

They also serve who only stand and wait.

This must be done, however contrary to our inclinations.

16. To separate words or phrases of direct address from the context.