812. As there is an ethereal medium by means of which light moves through space from the remotest visible fixed star to the eye, at the rate of two hundred thousand miles per second; as through an affection of the same ether frictional electricity moves, according to Wheatstone’s estimate, with a velocity exceeding that of light,—so may we not infer that the instrument of Divine will acts with still greater velocity, and that in making man in this respect after his own image, so far as necessary to an available existence, gives him one degree of power over the same element while in the mortal state, and another higher degree of power in the spiritual state. But if there be an element through which a spirit within his _mortal_ frame is capable of actuating that frame, may not this element of actuation be susceptible of becoming an instrument to the will of another spirit in the _immortal state_? 813. The aura of a medium which thus enables an immortal spirit to do within its scope things which it cannot do otherwise, appears to vary with the human being resorted to; so that only a few are so endowed with this aura as to be competent as media. Moreover, in those who are so constituted as to be competent instruments of spiritual actuation, this competency is various. There is a gradation of competency, by which the nature of the instrumentality varies from that which empowers violent loud knocking and the moving of ponderable bodies without actual contact, to the grade which confers power to make intellectual communications of the higher order without that of audible knocking. Further, the power to employ these grades of mediumship varies as the sphere of the spirit varies. 814. It has been stated that mortals have each a halo perceptible to spirits, by which they are enabled to determine the sphere to which any individual will go on passing death’s portal. Spirits cannot approach effectively a medium of a sphere much above, or below that to which they belong. 815. As media, in proportion as they are more capable of serving for the higher intellectual communication, are less capable of serving for mechanical demonstration, and as they are more capable of the latter are less competent for the former, spirits likewise have a higher or lower capacity to employ media. It has been mentioned that having made a test apparatus, my spirit sister alleged that it could not be actuated by her without assistance of spirits from a lower sphere. I inquired whether she could not meet me again, accompanied by the requisite aid. The reply was in the affirmative, and accordingly she met me at an appointed hour, and my apparatus was actuated effectually under test conditions. (Plate 4, _dd_, _ii_, _kk_.)