what was the method used by jerome to get kettle boiling?

They hat to boil the kettle at the nose of the boat and not look at it. "We put the kettle on to boil, up in the nose of the boat, and went down to the stern and pretended to take no notice of it, but set to work to get the other things out.

That is the only way to get a kettle to boil up the river. If it sees that you are waiting for it and are anxious, it will never even sing. You have to go away and begin your meal, as if you were not going to have any tea at all. You must not even look round at it. Then you will soon hear it sputtering away, mad to be made into tea."