"Faster than fairies, faster than witches." The repeated "f" sounds are an example of

Faster than fairies, faster than witches,
Bridges and houses, hedges and ditches;
And charging along like troops in a battle
All through the meadows the horses and cattle:
All of the sights of the hill and the plain
Fly as thick as driving rain;
And ever again, in the wink of an eye,
Painted stations whistle by.

Here is a child who clambers and scrambles,
All by himself and gathering brambles;
Here is a tramp who stands and gazes;
And here is the green for stringing the daisies!
Here is a cart run away in the road
Lumping along with man and load;
And here is a mill, and there is a river:
Each a glimpse and gone forever!