"Reminiscent of Aristotle, Jabir proposed... two exhalations: "earthy smoke" (small particles of earth on their way to becoming fire) and "watery vapor" (small particles of water on their way to becoming air). These, he believed, mingled to become the metals. But Jabir modified the Aristotelian approach by proposing that exhalations underwent intermediate transformations into sulfur and mercury before becoming metal. The reason for the existence of different types of metals, he believed, was that the sulfur and mercury were not always pure. He proposed that if the right proportions of sulfur and mercury with the right purity could be found... gold would result."