I wonder if the rounders that Catherine used to play is the same rounders that I played as a kid.

Rounders is a popular game for primary school kids here in Australia. We used to play it until we were old enough to play baseball. I remember it being similar to baseball, except you used a miniture sized cricket bat, and a tennis. This ment that the ball was easier to hit, and not as painful if it hit you instead. It was also deemed more suitable for being able to play with a class of both boys and girls. It's a good game for young kids aged 7-10, and possibly more fitting of a regency era girl. In a way it softens up the hard tomboy image you might have of Catherine, because it's not as physically demanding as other sports, but still gives an image of her being an active, sporty girl.