Off from the rigorous structure of a limerick, which usually has 9, 9, 6, 6, 9 syllables, and the stress pattern is usually anapests or amphibrachs. It's not considered a bad thing for the words to feel forced into their stress pattern, as that's common and sometimes thought of as somewhat essential.

As to story, I really don't know. I don't know why heliocentrism is singled out as something Holmes is trying to forget, and I'd take the poem more from Watson's point of view is accusing Holmes of "trying" to forget it, since it doesn't seem like he'd actually want to. Then in the end, it's really going to hinge on the reader recognizing what's honestly a very obscure name these days. Knowing Holmes, I figured it must be a composer or violinist, and it turns out to be both, but I'm a classical music aficionado, and I had only vaguely heard the name before. Not that it would fit a limerick well, but wasn't Holmes more obsessed with Beethoven's violin concerto? I like the idea, but it's pretty esoteric.