The macrocosmic and microcosmic fires are constantly circulating in nature, in what is called the Fountain of Nature or the rotation of the elements. When the heavenly fire coagulates or condenses, it forms an invisible and highly subtle moisture – the philosophical element of air. The process continues and the element of air condenses into the element of water, which in turn condenses to the element of earth where it is reinforced and joined to the central fire. The trapped central fire reverses the process, so that the soil is made volatile and becomes a thick water. The water is made volatile and evaporated into air, which is refined into the fire element, which in turn is regenerated by the heavenly fire, after which the cycle begins again. The two fires of the fountain together express the philosophical salt. Thus fire and air come into the waters and impregnate them; the waters get rid of their thickest part and give it to the earth. Thus the earth is heavy or saturated, and its abundance of earth and water is volatised and sublimated again upward by fire as steam, whose ascending and descending God has entrenched in the universal fire as the great and only agent of nature. Aurea Catena Homeri (1781) - Alchemy - The divine work