Omit periods after per cent, and after roman numerals when used strictly as figures, but not when used in names, as Napoleon III.
Use em dash in conversations such as this:
Mr. Smith—Is your task completed?
Mr. Brown—Nearly.
[62.] Punctuation with Parentheses. The comma should usually go after the last parenthesis; it is seldom needed before the first one. De Vinne says: “When any complete sentence is enclosed by parentheses, the period should be before the last parenthesis, but when these parentheses enclose a few words at the end of a sentence, the period should be after the last parenthesis.”
[63.] Medieval and such words are spelled the simplest way. See the Standard Dictionary. Subpena, diarrhea, Etna Company.
[64.] O, Oh, Oh! These expressions are punctuated thus: O for a South Sea home! O that I had insured in the Etna! Oh, how my tooth aches! Oh! my crimes are deep and dark.
[65.] Plural of Proper Names. It is a common newspaper error to run sentences like this, from the social columns of the San Francisco Examiner of July 15, 1906: “The Thomas H. Williams have been visiting the City.” The attempt to make the singular do the duty of the plural in such a case is ridiculous. Williamses is the plural of Williams. Printers and writers should learn how to write the plural of proper names.
[66.] Quote-marks. It is sometimes a puzzle where to place quote-marks. There is no better rule than that stated by De Vinne, who says that the closing marks of quotation always should be placed after the comma or the period in all places where these marks are needed; but the fact is the proper place of the closing marks of quotation should be determined by the quoted words only; they must inclose those words, and no more; they may be before or after the points, according to the construction of the sentence. When the quotation makes a complete sentence, put the quotation-marks after the period at the end of that sentence; when the quotation is at the end of but a portion of this sentence which terminates with a colon, semicolon, or any other point, then put the marks before the point. The mark of punctuation intended to define the construction of the completed sentence should not be made a portion of the fragmentary quoted matter.
A fine example of this is seen in the following: He asked, “Who said my mother lied?” and didn’t Jones reply, “Nobody dared to say that”?
[67.] Smaller Type. Quote-marks are not needed when extracts or quotations are set in smaller type than the body of the book or paper. Some reputable publications do not quote the extracts, even when they are set in the regular type of the publication and run in separate paragraphs. The indenting of the matter one em at the beginning and one em at the end of a line suffices. Such matter should be set solid when the main text is leaded.