Now though this is not exactly the way in which clairvoyance works, the theory is nevertheless quite true in most of its premises. Every object undoubtedly is throwing off radiations in all directions, and it is precisely in this way, though on a higher plane, that the akashic records seem to be formed. Of them it will be necessary to say something under our next heading, so we will do no more than mention them for the moment. The phenomena of psychometry are also dependent upon these radiations, as will presently be explained. There are, however, certain practical difficulties in the way of using these etheric vibrations (for that is, of course, what they are) as the medium by means of which one may see anything taking place at a distance. Intervening objects are not entirely transparent, and as the actors in the scene which the experimenter tried to observe would probably be at least equally transparent, it is obvious that serious confusion would be quite likely to result. The additional dimension which would come into play if astral radiations were sensed instead of etheric would obviate some of the difficulties, but would on the other hand introduce some fresh complications of its own; so that for practical purposes, in endeavouring to understand clairvoyance, we may dismiss this hypothesis of radiations from our minds, and turn to the methods of seeing at a distance which are actually at the disposal of the student. It will be found that there are five, four of them being really varieties of clairvoyance, while the fifth does not properly come under that head at all, but belongs to the domain of magic. Let us take this last one first, and get it out of our way. 1. _By the assistance of a nature-spirit._--This method does not necessarily involve the possession of any psychic faculty at all on the part of the experimenter; he need only know how to induce some denizen of the astral world to undertake the investigation for him. This may be done either by invocation or by evocation; that is to say, the operator may either persuade his astral coadjutor by prayers and offerings to give him the help he desires, or he may compel his aid by the determined exercise of a highly-developed will.