Sandburg's Fog

A poem does not have to be long nor laden with abstraction to create a powerful image. For example, though Carl Sandburg's poem, Fog, contains only six lines, and most of its words are one syllable, it creates a vivid image of fog.

The one thing about the poem that puzzles me is why, in line 5, Sandburg uses the word "silent" rather than words that imply silence, as he did in the first two lines.

Fog
by Carl Sandburg

The fog comes
on little cat feet.

It sits looking
over harbor and city
on silent haunches
and then moves on.