Carl Sandberg is describing the pleasant feeling of being shrouded in fog and how it arrives gently, sits for awhile then moves on so is unobtrusive whereas Robert Frost in Mending Wall there is a strong skepticism about his neighbour's dictum that "good walls make good neighbours" and his feelings of misgivings about maintaining a wall between adjacent properties when there are no cows to corral or no obvious practical reasons for the wall.
