Expose a towel or cloth to a strong fire till it becomes very hot; carry
it into a dark room, and, while it is cooling, throw upon it some grains
of gunpowder, which will at first inflame. Leave it to cool a little,
till the powder no longer detonates. If you then cover it with fresh
powder, the latter, when it acquires the same heat as the cloth, will
emit in the dark a faint light or weak flame, which will consume all the
sulphur without causing the nitre to detonate.