"If you build a big enough lens, you can get moonlight to start a fire."

Ah... I don't think so. Moonlight is just reflected glow-light -- it just doesn't have the "candlepower" that the sun does.

Also, what I don't understand about ice lenses is how to get clear ice. If it's cloudy ice (the only kind I can make <img src="/images/graemlins/crazy.gif" alt="" />), I don't see how it can focus light. I actually tried making two ice cubes in half-sphere molds (5" dia), then "gluing" them together with water, but I couldn't get it to focus, and that was on the 4th of July at high noon. (I figured if I couldn't do it then, I couldn't do it in MN in January.)

Sue