The Secret Work of the Hermetic Philosophy

118Let the furnace be round, its interior height about two feet. In its middle place a round iron or bronze plate as thick as the back of a knife, nearly spanning the interior width of the furnace but slightly narrower so that it does not touch the walls. Let it rest on three or four iron supports fixed to the walls, and be pierced with numerous holes, so that heat may rise more easily through them and between the sides of the furnace and the edges of the plate. Leave a little door below the plate and another above it in the furnace walls, so that fire may be placed beneath through the lower one, while the temper of the heat is perceived by the senses through the upper one. Opposite the latter make a small, glazed, rhomboid window, so that light from the other side may indicate the heats when the eye is brought to it. On the centre of the aforesaid plate place the tripod of secrets with its double vessel. Finally, cover the furnace thoroughly with its continuous, closely fitting vault or roof, closing the little doors tightly as well, so that the heat does not escape.