QUOTE(melech @ Dec 21 2007, 04:25 PM)

The Tur says you can't start a fire using wood or stones, which is fine. But then the Tur says nor with water such as when one places water in a glass container held against the sun and you used that to start a fire. How does that work exactly?
You never burned ants with a magnifying glass as a kid???
The water is like a lens I presume...