OK, the whole purpose of the puzzles on this island is to create a HUGE rollercoaster, with a ball going completely around the island through all four puzzles. You have to get each puzzle working properly so the ball can get through that 'stage' and on to the next.

Also, when you solve each puzzle, you'll get a hex code which you enter right near where you start out. This will enable the ramps for you to get up into the center of the roller coaster. Note that YOU get to be in the ball for its final run!! This is perhaps one of the coolest parts of the entire game :)

The Myst 3: Exile Walkthrough