You can occasionally use a dash to separate
part of a sentence and thus draw attention to it, just as you would with
a dramatic pause in speech. The dash forces your readers to momentarily
reflect on what precedes the dash—and then flings them into what
follows.
New York is a city
ripe with extremes—of wealth and poverty, of creative energy
and rage.
Without the dash, the reader would have
trouble disentangling with extremes of wealth from
of wealth and poverty. With it, city ripe with extremes
is clearly articulated from the elaborations: of wealth
and poverty, of creative energy and rage.
So there's the mess—to
date.
The vagabonds went on to Cuzco, an ancient city—or,
rather, two or three different cities piled one on top of another.
Although Kuusisto's love for poetry can result in
patches of overly self-conscious prose—"my soul crawls
around like a snail exploring a piece of broken glass"—he
is a powerful writer with a musical ear for language and a gift
for emotional candor.