The Fresnel Lense in an ingenious piece of kit and everyone should add one to their firelighting kit. You may need some Sun to use it but boy does it work quick on tinder!
The picture displayed was taken late one evening with a dwindling sun with not a lot of heat in it and it started the leaf smouldering in a second - Yes, 1 second!!
The lense is simply a thin, flat piece of plastic that has a the lense ingeniously inscribed onto it, hold it at the correct distance to concentrate and project the Suns rays onto some tinder in one tiny spot and Hey Presto - fire.
It really is that simple. Just experiment with which types of tinder work the best and with a little practice it is second nature. We have found that dried leaves or dried grass works best which is everywhere!