Joanna Bird: Equilibrium

My chimney is rather more sooty than fiery;
A tradesman is booked in to give it a clean,
But when the appointment was made in the diary,
The day was a Friday, the date was thirteen:

A date that is commonly thought inauspicious,
A day when mischance has traditionally struck,
And yet, then again (if I’m so superstitious),
Chimney sweeps generally herald good luck.

I’ve done calculations (mathematically formal)
And luck that’s conflicting should just counteract,
So if the day turns out to be pretty normal
My theory will prove to be verified fact.

Three dark red cylindrical chimneypots