6. To separate a long subject from the verb of the predicate. Thus,—
To have passed them over in an historical sketch of my literary life and opinions, would have seemed to me like the denial of a debt.—Coleridge.
7. To set off an appositive noun or an appositive adjective, with its modifiers. Thus,—
I have had the most amusing letter from Hogg, the Ettrick minstrel.
There was an impression upon the public mind, natural enough from the continually augmenting velocity of the mail, but quite erroneous, that an outside seat on this class of carriages was a post of danger.—De Quincey.
Note 1. Many participial and other adjective phrases come under this head. Thus,—
The genius, seeing me indulge myself on this melancholy prospect, told me I had dwelt long enough upon it.—Addison.
Note 2. If a noun and its appositive are so closely connected as to form one idea, no comma is used. Thus,—
My friend Jackson lives in San Francisco.
Note 3. An intensive pronoun (myself, etc.) is not separated by a comma from the substantive which it emphasizes.
Note 4. A series of words or phrases in apposition with a single substantive is sometimes set off, as a whole, by a comma and a dash.