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 there 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.
-- R.L.STEVENSON

What is the main purpose of the above poem?