[PW] 'Ough' poem?

[JT Thompson]

Wombats, step up to the womplate and help: long ago, in a long 
forgotten book there was an introduction which quoted a poem based on 
the pronunciation of 'ough'.

It was in the voice of a Frenchman trying to learn English, and each 
'ough' word rhymed incorrectly with the pronunciation of the 'ough' 
word in the previous rhyme-line. It ended 'I killed him with a rough' 
(to rhyme, of course, with 'lough').

Can anyone identify the poem?