There are many similar cases--similar, I mean, not in the possession of that particular form of sight (which is unique in my experience), but in showing the development of some one small part of the full and clear vision of the astral and etheric planes. In nine cases out of ten, however, such partial clairvoyance will at the same time lack precision also--that is to say, there will be a good deal of vague impression and inference about it, instead of the clear-cut definition and certainty of the trained man. Examples of this type are constantly to be found, especially among those who advertise themselves as "test and business clairvoyants." Then, again, there are those who are only temporarily clairvoyant under certain special conditions. Among these there are various subdivisions, some being able to reproduce the state of clairvoyance at will by again setting up the same conditions, while with others it comes sporadically, without any observable reference to their surroundings, and with yet others the power shows itself only once or twice in the whole course of their lives. To the first of these subdivisions belong those who are clairvoyant only when in the mesmeric trance--who when not so entranced are incapable of seeing or hearing anything abnormal. These may sometimes reach great heights of knowledge and be exceedingly precise in their indications, but when that is so they are usually undergoing a course of regular training, though for some reason unable as yet to set themselves free from the leaden weight of earthly life without assistance. In the same class we may put those--chiefly Orientals--who gain some temporary sight only under the influence of certain drugs, or by means of the performance of certain ceremonies. The ceremonialist sometimes hypnotizes himself by his repetitions, and in that condition becomes to some extent clairvoyant; more often he simply reduces himself to a passive condition in which some other entity can obsess him and speak through him. Sometimes, again, his ceremonies are not intended to affect himself at all, but to invoke some astral entity who will give him the required information; but of course that is a case of magic, and not of clairvoyance. Both the drugs and the ceremonies are methods emphatically to be avoided by any one who wishes to approach clairvoyance from the higher side, and use it for his own progress and for the helping of others. The Central African medicine-man or witch-doctor and some of the Tartar Shamans are good examples of the type.