Thanks. That's not bad. It's just that someone claimed it was an example of Zeugma, whcih it is not. He now wants to know waht it actually is. Isn't just a metaphor is it?
No, a metaphor would indicate that there is a similarity between the kettle and the water, which there isn't, a metonym works because there is an association between the kettle and the water.
It may also be described as a transferred epithet, which perfectly describes the situation...ie the water not the kettle is boiling. The phrase, 'the condemned cell', is another good illustration of this particular figure of speech; it is the prisoner within who is condemned, not the cell.
I meant to add that "She went home in a flood of tears and a sedan chair" is an example of zeugma/syllepsis...ie one verb or adjective being rather inappropriately used to apply to two different nouns/noun phrases.