Now, it would appear rational to suppose that some action of this sort takes place when mind acts upon, or influences, matter. Air is invisible, and practically imperceptible to our senses--_when stationary_. But set into motion, a current of air will close a door with a bang--will have the effect of definitely moving a heavy mass of inanimate matter, in the manner indicated. It may be that in somewhat the same way mind affects brain. Mind may reside in a sort of etheric vehicle, and be more or less stable or stationary, save at the times when volition or intense, active conscious operations are in progress--when, in short, _effort_ is exerted. At such times, it is surely conceivable that what was static becomes dynamic; something is set into motion which in turn brings into activity some more "physical" energy, and so on, until sufficient material momentum has been gained to affect that most unstable and mobile substance, nervous tissue. It is certainly quite conceivable that certain nervous centres in the brain (_which_ centres, we cannot say) might be set into actual operation by some such process; or at least that the impulse or energy supplied in this manner might be sufficient to release the nervous energy stored in the cell, much as the trigger of a rifle would, when pressed, release the energy contained within the cartridge. Such "hair trigger" action has been postulated by both William James and Bergson, and is certainly in line with modern speculations in this direction. There are also certain analogies to be drawn from physical science to guide us here. In electricity, e.g., what are known as "relays" are constantly employed, and beautifully illustrate the principle here outlined. In working over long lines, or where there are a number of instruments in one circuit, the currents are often not strong enough to work the recording instruments directly. In such a case there is interposed a "relay" or "repeater." This instrument consists of an electro-magnet round which the line current flows, and whose delicately-poised armature, when attracted, makes contact for a local circuit, in which a local battery and the receiving Morse instrument (sounder, writer, etc.) are included. The principle of the relay is, then, that a current too weak to do the work itself may get a strong local current to do its work for it. It may be the same in the case of mental action. Volition or thought may be too weak, _per se_, to influence nervous processes; but, when exceptionally active or potent, they may set into activity specific nerve energies which manifest in the manner known to us as motor and physical phenomena. Here is, it seems to me, a rational explanation of the facts, and one which is in accord, not only with ordinary psychological phenomena, but with those more puzzling and obscure manifestations witnessed from time to time in psychic research.