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. To express in one sentence great contrariety of action or emotion or to increase the speed of the discourse by a succession of snappy phrases.
She starts—she moves—she seems to feel
The thrill of life along her keel.