The dash is a very useful mark which has been greatly overworked by careless writers. It is very easy to make in manuscript and serves as a convenient cover for the writer’s ignorance of what point should properly be used.
The conspicuousness of the dash makes it a very useful mark for guiding the eye of the reader to the unity of the sentence. It is particularly useful in legal pleadings where there is much repetition of statement and great elaboration of detail. In such cases commas, semicolons, and even parentheses are so multiplied that the relation of the clauses is lost sight of. The confusion thus arising may often be cleared up by intelligent use of the dash.
The dash is sometimes used to connect a side heading with the text that follows, or to connect the end of that text with the name of the writer.
A Rule for Peace.—If it be possible, as much as lieth in you, live peaceably with all men.—St. Paul.
The dash is sometimes used in catalogue work as a ditto mark.
De Vinne, Theodore Low. Historic Printing Types. New York, 1886.
——The Invention of Printing. Francis Hart & Co., New York, 1878.
——Plain Printing Types. Oswald Publishing Co., New York, 1914.
French printers use the dash in printing dialogue as a partial substitute for quotation marks. Quotation marks are placed at the beginning and end of the dialogue and a dash precedes each speech. This form is used even if the dialogue is extended over many pages.