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.
In this connection DeVinne gives the following excellent example from Sterne: Nature instantly ebbed again;--the film returned to its place;--the pulse fluttered,--stopped,--went on,--throbbed,--stopped again,--moved,--stopped,--Shall I go on ?--No.
Attention may be called to Sterne's use of the semicolon and the comma with the dash, a use now obsolete except in rare cases.
4.

To separate the repetition or different amplifications of the same statement.
The infinite importance of what he has to do--the goading conviction that it must be done--the dreadful combination in his mind of both the necessity and the incapacity--the despair of crowding the concerns of an age into a moment--the impossibility of beginning a repentance which should have been completed--of setting about a peace which should have been concluded--of suing for a pardon which should have been obtained--all these complicated concerns intolerably augment the sufferings of the victims.
5.

At the end of a series of phrases which depend upon a concluding clause.
Railroads and steamships, factories and warehouses, wealth and luxury--these are not civilization.
6.

When a sentence is abruptly terminated.
If I thought he said it I would-- 7.

To precede expressions which are added to an apparently completed sentence, but which refer to some previous part of the sentence.
He wondered what the foreman would say--he had a way of saying the unexpected.
8.