When I was a child a rather

Slow and Dirty railway

Passed behind my house

I enjoyed watching the trains

From my bedroom window

And then my father

Took a job in Amerika

And I did not visit England

For twelve long years

We later returned to our previous house

However the Slow and Dirty railway

Was now populated by rapid expresses

It was then that I realised

That the speed and frequency of these trains

In theory made them invisible

And time was the only constant factor