I like David's solution and I am in awe of his stone-cutting capability.
However, to return to your problem where the ellipse has been returned
without any markings, why not draw an ellipse of the same specified
dimensions on paper with the axes already marked on it? This could then be
matched to
Dear Karl,
Your idea is not without merit:
> Wrap the slate with a reflective strip ...
> Playing around with a laser should find the
> focii.
This is sometimes referred to as the
"Elliptical Billiard Table Problem"...
If you aim at a focus, the laser path will
reflect through the other focus
I cut my own slate ellipses, often up to 3cm thick. In the process of
marking out the ellipse I will have drawn both the major and minor axes.
I make a small indentation with a metal scribe at both ends of both axes
as well as the centre point. These indentations are deep enough to be
