The stresses in the lines are what is called an anapestic metric foot, meaning two unstressed syllables followed by a stressed syllable: da-da-DAH-da-da-DAH-da-da-DAH,* da-da-DAH-da-da-DAH-da-da ...
For those that like to know this sort of thing, the rhythm of the limerick is officially described as 'anapestic trimeter'... demonstrated by Lear's: And played several tunes with her chin.
Written in anapestic tetrameter, the book was test-read by over 200 children and has proved popular with 1,000 copies sold and an endorsement from Dame Joanna Lumley. Dame Joanna Lumley said ...