The sequence of discs attached immediately to the left
of the main cardioid correspond to a stable 2cycle,
4cycle, 8cycle, ..., and so is called the
perioddoubling cascade. 
Here we measure the diameters of the components in
order to discover a pattern in how the components shrink. 
The limit of the ratios of the diameters of successive compnents
is an instance of the Feigenbaum scaling. 
The HurwitzRobucci scaling is an interesting example
because it scaling equation can be solved exactly and the scaling ratio derived. 
Return to the Mandelbrot set and Julia sets.
