This book purports to be about the Urim and Thummim, the symbolic breastplates of the Jewish High Priests. It is, however, a detailed alchemical perspective on Fire and Light, two complementary aspects in the creation of metals. It explains in great detail how the two complementary alchemical substances, Sulphur and Mercury, work to produce the veins of metals in the mines under the Earth, and how an alchemist can work these processes in his flasks in the laboratory. It is primarily concerned with making of gold using the Philosophers' Stone.