Various explanations of the power employed by the spirits, assisted by
the medium and by the circle, have been offered by the scientific
investigators of the subject. The most generally accepted theory of the
western scientists is that the spirits employ what is called the
"psychic force" of the medium, often assisted by that drawn from the
circle and focused in the medium. The medium is regarded as a psychic
storage battery which is freely drawn upon by the manifesting spirit.
The degree and character of the manifestations are determined largely by
the peculiar quality of the psychic force, the capabilities of the
medium, the knowledge and powers of the spirits, and the influence of
the sitters.

Human Magnetism.

Dr. Dean Clarke says: "Human magnetism, or nerve aura, is probably the
most sublimated form of ethereal matter, hence nearest in refinement to
spirit substance, and therefore spirits use it as the vehicle of their
vibrating forces. Those persons who have an excess of magnetism, of the
proper quality to unite with both the psychic force of spirits and the
forces inherent in natural objects, and thus form an electro-magnetic
connection of spirits with the objects they wish to act upon, are the
persons chosen by the spirits for physical mediums. The mind and brain
of the medium are not often nor necessarily controlled, and only his
magnetism and psychic forces are used, through which the spirits
transmit the vibrations of their own power to mechanically produce
concussions, or movements of material objects."

"Zoether."

Hudson Tuttle (writing under control) gives the following statement of a
spirit concerning the manner in which physical phenomena are produced:
"Zoether (psychic force) emanating from the medium charges the object to
be moved, and a band of spirits directs a current of their own zoethic
emanation in the direction they desire the article to move, and it
passes along the current thus produced. The charging of the object by
the medium is necessary in order that it may be in a state of vibration
harmonious to the spirit current. If this current be directed against
the table or other charged body, raps or concussions are produced, as a
positive and negative relation exists between the spirits and the
medium's zoether. One spirit alone cannot produce physical
manifestations. If one purports to communicate, assistance will be
rendered by many others, who combine their influence."

"Pran