To Set Fire To A Combustible Body By Reflection
Place two concave mirrors at about twelve feet distance from each
other, and let the axis of each be in the same line. In the focus of
one of them place a live coal, and in the focus of the other some
gunpowder. With a pair of strong bellows keep blowing the coal, and
notwithstanding the distance between them, the powder will presently
take fire.
The mirror may be either made of glass, metal, or pasteboard gilt.