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.
_Rules for the Use of the Dash_ 1.

To mark abrupt changes in sentiment and in construction.
Have you ever heard--but how should you hear?
2.

To mark pauses and repetitions used for dramatic or rhetorical effect.
They make a desert, and call it--peace.
Thou, great Anna, whom three states obey, Who sometimes counsel takes--and sometimes tea.
3.