Read the following poem and answer the question that follow :
Whose woods are these I think I know
His house is in the village though
He will not see me stopping here
To watch his woods fill up with snow
My little horse must think queer
To stop without a farmhouse near
Between the woods and the frozen lake
The darkest evening of the year.
He gives his harness bells a shake
To ask if there is some mistake
The only other sound is the sweep
Of easy wood and downy flake.
The figure of speech used in 'dark and deep ' is :