A budding young preacher from a larger city church was despatched to a small country congregation to perform rotational duties. Upon arriving at the church he entered and was met by a crusty gentleman who was busily feeding wood into a pot-belly stove in the middle of the quite old and somewhat chilly chapel. Plucking up courage he eventually asked what would be the order of the service, "well, said the local, after we sing some songs you gets up and preaches"
For how long should I speak? asked the nervous young man
Well that's easy responded the other. Now you see that pot-belly, and you see this kettle, when you gets up to preach I puts this kettle on that pot-belly, and when the kettle boils its time to stop preaching, and we all have a cup of coffee.
And how long does that take? enquired the young man
Well it's about 25 minutes if I fill the kettle, he said, but for some preachers, I only half fills it.