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.
This method has been largely practised in the East (where the entity employed is usually a nature-spirit) and in old Atlantis, where "the lords of the dark face" used a highly-specialized and peculiarly venomous variety of artificial elemental for this purpose. Information is sometimes obtained in the same sort of way at the spiritualistic séance of modern days, but in that case the messenger employed is more likely to be a recently-deceased human being functioning more or less freely on the astral plane—though even here also it is sometimes an obliging nature-spirit, who is amusing himself by posing as somebody's departed relative. In any case, as I have said, this method is not clairvoyant at all, but magical; and it is mentioned here only in order that the reader may not become confused in the endeavour to classify cases of its use under some of the following headings.
2. By means of an astral current.—This is a phrase frequently and rather loosely employed in some of our Theosophical literature to cover a considerable variety of phenomena, and among others that which I wish to explain. What is really done by the student who adopts this method is not so much the setting in motion of a current in astral matter, as the erection of a kind of temporary telephone through it.
It is impossible here to give an exhaustive disquisition on astral physics, even had I the requisite knowledge to write it; all I need say is that it is possible to make in astral matter a definite connecting-line that shall act as a telegraph-wire to convey vibrations by means of which all that is going on at the other end of it may be seen. Such a line is established, be it understood, not by a direct projection through space of astral matter, but by such action upon a line (or rather many lines) of particles of that matter as will render them capable of forming a conductor for vibrations of the character required.
This preliminary action can be set up in two ways—either by the transmission of energy from particle to particle, until the line is formed, or by the use of a force from a higher plane which is capable of acting upon the whole line simultaneously. Of course this latter method implies far greater development, since it involves the knowledge of (and the power to use) forces of a considerably higher level; so that the man who could make his line in this way would not, for his own use, need a line at all, since he could see far more easily and completely by means of an altogether higher faculty.
Even the simpler and purely astral operation is a difficult one to describe, though quite an easy one to perform. It may be said to partake somewhat of the nature of the magnetization of a bar of steel; for it consists in what we might call the polarization, by an effort of the human will, of a number of parallel lines of astral atoms reaching from the operator to the scene which he wishes to observe. All the atoms thus affected are held for the time with their axes rigidly parallel to one another, so that they form a kind of temporary tube along which the clairvoyant may look. This method has the disadvantage that the telegraph line is liable to disarrangement or even destruction by any sufficiently strong astral current which happens to cross its path; but if the original effort of will were fairly definite, this would be a contingency of only infrequent occurrence.
The view of a distant scene obtained by means of this "astral current" is in many ways not unlike that seen through a telescope. Human figures usually appear very small, like those on a distant stage, but in spite of their diminutive size they are as clear as though they were close by. Sometimes it is possible by this means to hear what is said as well as to see what is done; but as in the majority of cases this does not happen, we must consider it rather as the manifestation of an additional power than as a necessary corollary of the faculty of sight.
It will be observed that in this case the seer does not usually leave his physical body at all; there is no sort of projection of his astral vehicle or of any part of himself towards that at which he is looking, but he simply manufactures for himself a temporary astral telescope. Consequently he has, to a certain extent, the use of his physical powers even while he is examining the distant scene; for example, his voice would usually still be under his control, so that he could describe what he saw even while he was in the act of making his observations. The consciousness of the man is, in fact, distinctly still at this end of the line.
This fact, however, has its limitations as well as its advantages, and these again largely resemble the limitations of the man using a telescope on the physical plane. The experimenter, for example, has no power to shift this point of view; his telescope, so to speak, has a particular field of view which cannot be enlarged or altered; he is looking at his scene from a certain direction, and he cannot suddenly turn it all round and see how it looks from the other side. If he has sufficient psychic energy to spare, he may drop altogether the telescope that he is using and manufacture an entirely new one for himself which will approach his objective somewhat differently; but this is not a course at all likely to be adopted in practice.
But, it may be said, the mere fact that he is using astral sight ought to enable him to see it from all sides at once. So it would if he were using that sight in the normal way upon an object which was fairly near him—within his astral reach, as it were; but at a distance of hundreds or thousands of miles the case is very different. Astral sight gives us the advantage of an additional dimension, but there is still such a thing as position in that dimension, and it is naturally a potent factor in limiting the use of the powers of its plane. Our ordinary three-dimensional sight enables us to see at once every point of the interior of a two-dimensional figure, such as a square, but in order to do that the square must be within a reasonable distance from our eyes; the mere additional dimension will avail a man in London but little in his endeavour to examine a square in Calcutta.