How do these lines develop the theme that nature has power over human efforts? They compare snow to a natural substance (wool) and illustrate it covering the road, a symbol of human progress.

They suggest either snow or rain, but the deeper meaning of decay over time is clear, too.

They depict a lot of rain from a leaden (gray) sky that smooths the wrinkles in an old dirt road.

They suggest the madness that eventually overtook the author of the poem.