THE APOSTROPHE
There are but few uses of the apostrophe, and they are well settled, as follows:
1. To indicate the omission of letters or figures in contractions: ne’er, don’t, it’s (it is), ’t will, class of ’83, the gold-seekers of ’49, etc.
2. To indicate the possessive case of nouns, but not of pronouns: Henry’s, man’s, Jones’s, a boy’s task, the boys’ play-ground, for conscience’ sake, etc.
3. To indicate, with s, the plurals of letters, figures, symbols, and certain unusual or peculiar names: i’s and t’s, 6’s and 7’s, four t’s, several D.D’s, the stay-at-home’s, etc.