In the poem ‘Fog’ Carl Sandburg has metaphorically compared th fog to a cat. The first strange thing about the metaphor is the comparison of a phenomenon with a living animal. Perhaps the poet wants to emphasize the silent nature and mysterious ways of the fog, so he has compared the fog to a cat. A cat does not make a sound when it walks. So also is the fog, but its presence is apparent.
Its “silence” is very much like that of a cat moving on its little feet. Then the fog stays in its place looking over the harbour and city which creates a hazy atmosphere all around. The way it sits is very much like a cat sitting on its haunches, looking here and there before it makes a move. This is as if the for remains a silent spectator of the happenings in the city. Whatever the purpose may be, both the fog as well as a cat make their impression and make their presence felt. The comparison of the fog to a cat seems very appropriate because, reading the poem, one feels that truly, the fog approaches stealthily, just like a cat.