A reverse fountain is to the normal fountain
what a reverse cascade
is to a normal cascade
; the balls move in the opposite direction, as if you had recorded a tape and then played it backwards.
To do a reverse fountain, just start the regular four ball fountain, and then change the throws from inside-to-out to outside-to-in. (i.e. your right hand will now be throwing anti-clockwise instead of clockwise, and vice versa for your left.)
Easy enough in theory. In practice, however, the whole pattern has the nasty tendancy to contract inwards after a short while, until the balls hit each other and you drop everything.
Control! You must learn control! Keep the hands moving outwards to throw, as well as inwards to catch.
The reverse fountain is one of those patterns that you learn in a flash just after you master the four ball fountain. The other one, of course, is pistons. But don't play their importance down... any four ball pattern is good practice for... <shudder>... five balls.
Technically, a reverse fountain can also mean with six or eight balls as well... but then with more balls, the transition from one pattern to another becomes more complicated (more opportunities for balls to hit each other), and if you're really that good, shouldn't you be working on your next ball?