Evans-Wentz, W Y - Alchemical and Mystical Theory 
Type of Spiritual Experience
The 'gnome' classification and naming is not, I think, quite correct, but the main classes are there
A description of the experience
Alchemical and Mystical Theory
In the positive doctrines of mediaeval alchemists and mystics, e.g. Paracelsus and the Rosicrucians, as well as their modern followers, the ancient metaphysical ideas of Egypt, Greece, and Rome find a new expression; and these doctrines raise the final problem--if there are any scientific grounds for believing in such pygmy nature-spirits as these remarkable thinkers of the Middle Ages claim to have studied as beings actually existing in nature.
These mediaeval metaphysicians, inheritors of pre-Platonic, Platonic, and neo-Platonic teachings, purposely obscured their doctrines under a covering of alchemical terms, so as to safeguard themselves against persecution, open discussion of occultism not being safe during the Middle Ages, as it was among the ancients and happily is now again in our own generation. But they were quite scientific in their methods, for they divided all invisible beings into four distinct classes:
- The Angels, who in character and function are parallel to the gods of the ancients, and equal to the Tuatha De Danann of the Irish, are the highest; below them are
- The Devils, who correspond to the fallen angels of Christianity; the third class includes all
- Elementals, sub-human Nature-Spirits, who are generally regarded as having pygmy stature; and the fourth division comprises the
- Souls of the Dead, and the shades or ghosts of the dead.
For us, the third class, which includes spirits of pygmy-like form, is the most important in this present discussion.
All its members are of four kinds, according as they inhabit one of the four chief elements of nature.
- Gnomes - Those inhabiting the earth are called Gnomes. They are definitely of pygmy stature, and friendly to man, and in fairy-lore ordinarily correspond to mine-haunting fairies or goblins, to pixies, corrigans, leprechauns, and to such elves as live in rocks, caverns, or earth--an important consideration entirely overlooked by champions of the Pygmy Theory.
- Sylphs - Those inhabiting the air are called Sylphs. These Sylphs, commonly described as little spirits like pygmies in form, correspond to most of the fairies who are not of the Tuatha De Danann or 'gentry' type, and who as a race are beautiful and graceful. They are quite like the fairies in Shakespeare's Midsummer-Night's Dream; and especially like the aerials in The Tempest, which, according to Mr. Morton Luce, a commentator on the drama, seem to have been shaped by Shakespeare from his knowledge of Rosicrucian occultism, in which such spirits hold an important place.
- Nymphs - Those inhabiting the water are called Undines, and correspond exactly to the fairies who live in sacred fountains, lakes, or rivers.
- Salamanders - And the fourth kind, those inhabiting the fire, are called Salamanders, and seldom appear in the Celtic Fairy-Faith: they are supreme in the elementary hierarchies.
All these Elementals, who procreate after the manner of men, are said to have bodies of an elastic half-material essence, which is sufficiently ethereal not to be visible to the physical sight, and probably comparable to matter in the form of invisible gases.
The source of the experienceAlchemy
Concepts, symbols and science items