The crystal, etc., serves to focus the psychic energy of the person, in such a way that the astral senses are induced to function more readily than ordinarily. The student is cautioned against regarding the crystal, or magic mirror, as possessing any particular magic power in itself. On the contrary, the crystal, or magic mirror serves merely as a physical instrument for the astral vision, just as the telescope or microscope performs a similar office for the physical vision. Some persons are superstitious regarding the crystal, and accord to it some weird supernatural power, but the true occultist, understanding the laws of the phenomena arising from its use, does not fall into this error. But, notwithstanding what I have just said, I would be neglecting my full duty in the matter if I failed to call your attention to the fact that the continued use of a particular crystal often has the effect of polarizing its molecules so as to render it a far more efficient instrument as time passes by. The longer the crystal is used by one person, the better does it seem to serve the uses of that person. I agree with many users of the crystal in their belief that each person should keep his crystal for his own personal use, and not allow it to be used indiscriminately by strangers or persons not in sympathy with occult thought. The crystal tends to become polarized according to the requirements of the person habitually using it, and it is foolish to allow this to be interfered with. The use of crystals and other bright, shining objects, has been common to psychic investigators of all times, and in practically all lands. In the earlier days of the race, pieces of clear quartz or shining pebbles were generally employed. Sometimes pieces of polished metal were so used. In fact, nearly every object capable of being polished has been employed in this way at some time, by some person. In our own day, the same condition exists. In Australia the native sooth-sayers and magicians employ water and other shining objects, and, in some cases, even bright flame, sparks, or glowing embers. In New Zealand, the natives frequently employ drops of blood held in the hollow of the hand. The Fijians fill a hole with water, and gaze into it. South American tribes use the polished surface of black, or dark colored stones. The American Indians use water, or shining pieces or flint or quartz. Shining pieces of metal are frequently used by the primitive races. Lang, writing on the subject, has said: "They stare into a crystal ball; a cup; a mirror; a blot of ink (Egypt and India); a drop of blood (the Maoris of New Zealand); a bowl of water (American Indians); a pond (Roman and African); water in a glass bowl (Fez); or almost any polished surface, etc."