best to follow copy.
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.

I submit, gentlemen, to your judgment.
From today, my son, your future is in your own hands.

17. Between the name of a person and his title or degree.

Woodrow Wilson, President of the United States.
Charles W. Eliot, LL.D.

18. Before the word _of_ connecting a proper name with residence or
position.

Senator Lodge, of Massachusetts.
Elihu B. Root, Senator from New York.

19. After the salutatory phrase at the beginning of a letter, when
informal.

Dear John,

When the salutation is formal a colon should be used.

My dear Mr. Smith:

20. To separate the closing salutation of a formal letter from the rest
of the sentence of which it forms a part.

Soliciting your continued patronage, I am,
Very sincerely yours,
John W. Smith.

21. To separate two numbers.

January 31, 1915.
By the end of 1914, 7062 had been built.

22. To indicate an ellipsis.

Subscription for the course, one dollar.

Exceptions to this rule are made in very brief sentences, especially in
advertisements: Tickets 25 cents. Price one dollar.

The foregoing rules for the use of the comma have been compiled from
those given by a considerable number of authorities. Further examination
of authorities would probably have added to the number and to the
complexity of these rules. No two sets of rules which have come under
the writer's observation are alike. Positive disagreements in modern
treatises on the subject are few. The whole matter, however, turns so
much on the use made of certain general principles and the field is so
vast that different writers vary greatly in their statements and even in
their ideas of what ought to be stated. It is very difficult to strike
the right mean betwe