There seems to have been always and everywhere (or nearly so) a belief in a race, neither divine nor human, but very like to human beings, who existed on a 'plane' different from that of humans, though occupying the same space. This has been called the 'astral' or the 'fourth-dimensional' plane. Why 'astral'? why 'fourth-dimensional'? why 'plane'? are questions the answers to which do not matter, and I do not attempt to defend the terms, but you must call it something. This is the belief to which Scott refers in the introduction to _The Monastery_, as the 'beautiful but almost forgotten theory of astral spirits or creatures of the elements, surpassing human beings in knowledge and power, but inferior to them as being subject, after a certain space of years, to a death which is to them annihilation'. The subdivisions and elaborations of the subject by Paracelsus, the Rosicrucians, and the modern theosophists are no doubt amplifications of that popular belief, which, though rather undefined, resembles the theory of these mystics in its main outlines, and was probably what suggested it to them. These beings are held to be normally imperceptible to human senses, but conditions may arise in which the 'astral plane' of the elementals and that part of the 'physical plane' in which, if one may so express it, some human being happens to be, may be in such a relation to one another that these and other spirits may be seen and heard. Some such condition is perhaps described in the story of Balaam the soothsayer, in that incident when 'the Lord opened the eyes of the young man and he saw, and behold, the mountain was full of horses and chariots of fire round about Elisha', and possibly also in the mysterious 'sound of a going in the tops of the mulberry trees' which David heard; but no doubt in these cases it was angels and not elementals. It may also be allowable to suggest, without irreverence, that the Gospel stories of the Transfiguration and Ascension are connected with the same idea, though the latter is expressed in the form of the geocentric theory of the universe. The Cornish pisky stories are largely made up of instances of contact between the two 'planes', sometimes accidental, sometimes deliberately induced by incantations or magic eye-salve, yet with these stories are often mingled incidents that are not preternatural at all. How, when, and why this belief arose, I do not pretend even to conjecture; but there it is, and though of course the holders of it do not talk about 'planes', that is very much the notion which they appear to have.