Theory:

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.
Explanation:
 
The poem is set in a scene of train travel. As the poet saw outside his window, he says that the train travelled faster than imaginary characters like fairies (good angels) and witches (evil women).
 
fast train.jpg
The train was faster than fairies, faster than witches!
 
He says that the train travelled past many bridges and he was also able to see many houses on the way. There were abundant growth of shrubs and bushes along the way. There were also narrow channels of water along the side of the tracks.
 
train.jpg
There were hedges on the way!
 
The train rushed forward as if it were a group of soldiers marching ahead to attack! He saw that there were farms filled with hay to feed the horses and cows. He saw the plains and the hills moving continuously. It all went past him in a flying motion, as it were raindrops that were propelled by fast winds, especially during a storm. The train stations are usually painted bright and colourful to capture one's attention. There are guards in the station, who whistle to mark the passing of a train. Before he could finish a wink of his eye, he saw train stations also pass by - along with it the whistle sounds also passed by.
 
fast train 1.jpg
The painted stations whistled by, in a wink of an eye!
 
Meanings of difficult words:
  
No.
Words
Meanings
1
fairysmall imaginary female being that has magical powers
2
witcha woman thought to have magic powers, especially evil ones
3
hedgea boundary formed by closely growing bushes
4
ditcha narrow channel dug at the side of a road or track, to hold or carry away water
5
chargea headlong rush forward, typically in attack
6
troopssoldiers
7
meadowsa piece of grassland, especially one used for hay
8
wink of an eyeinstantly; used here to express time frame - it takes a second to close and open one's eyes
Reference:
State Council of Educational Research and Training (2019). Term-2 English Standard-6. From a Railway Carriage - R.L. Stevenson (pp. 128-131). Published by the Tamil Nadu Textbook and Educational Services Corporation.