(2) Air is, therefore, twofold in nature-tangible atmosphere and an intangible, volatile substratum which may be termed spiritual air. Fire is visible and invisible, discernible and indiscernible--a spiritual, ethereal flame manifesting through a material, substantial flame. Carrying the analogy further, water consists of a dense fluid and a potential essence of a fluidic nature. Earth has likewise two essential parts--the lower being fixed, terreous, immobile; the higher, rarefied, mobile, and virtual. The general term elements has been applied to the lower, or physical, phases of these four primary principles, and the name elemental essences to their corresponding invisible, spiritual constitutions. Minerals, plants, animals, and men live in a world composed of the gross side of these four elements, and from various combinations of them construct their living organisms.