The phenomenon of disintegration also may be brought about by the action of extremely rapid vibrations, which overcome the cohesion of the molecules of the object operated upon. A still higher rate of vibrations of a somewhat different type will separate these molecules into their constituent atoms. A body reduced by these means to the etheric condition can be moved by an astral current from one place to another with very great rapidity; and the moment that the force which has been exerted to put it into that condition is withdrawn it will be forced by the etheric pressure to resume its original form. It is in this way that objects are sometimes brought almost instantaneously from great distances at spiritualistic _seances_, and it is obvious that when disintegrated they could be passed with perfect ease through any solid substance, such, for example, as the wall of a house or the side of a locked box, so that what is commonly called "the passage of matter through matter" is seen, when properly understood, to be as simple as the passage of water through a sieve, or of a gas through a liquid in some chemical experiment. [Sidenote: Materialization.] Since it is possible by an alteration of vibrations to change matter from the solid to the etheric condition, it will be comprehended that it is also possible to reverse the process and to bring etheric matter into the solid state. As the one process explains the phenomenon of disintegration, so does the other that of materialization; and just as in the former case a continued effort of will is necessary to prevent the object from resuming its original form, so in exactly the same way in the latter phenomenon a continued effort is necessary to prevent the materialized matter from relapsing into the etheric condition. In the materializations seen at an ordinary _seance_, such matter as may be required is borrowed as far as possible from the medium's etheric double--an operation which is prejudicial to his health, and also undesirable in various other ways; and this explains the fact that the materialized form is usually strictly confined to the immediate neighbourhood of the medium, and is subject to an attraction which is constantly drawing it back to the body from which it came, so that if kept away from the medium too long the figure collapses, and the matter which composed it, returning to the etheric condition, rushes back instantly to its source. [Sidenote: Why Darkness is required.] [Sidenote: Spirit Photographs.]