They couldn't do it with a simple lens, but they did get enough heat to create smoke by using a sphere rather than a lens. The reason was that the lens rapidly lost its shape due to melting, whereas the sphere remained spherical enough for longer.
Monday, August 22, 2011 9:33:34 PM
In the meanwhile you have contracted hypothermia while waiting in the cold for the freaking sun to come out from the clouds. Learn from the Polynesians how to start fire. They can do it from wet wood in a tropical forest.