Should the glass of a vacuum tube or bulb be pervaded by the ether in the manner we have supposed it to be, and we believe there can be no doubt that it is so, it is obvious that its glowing when a current of electricity is passed through it must be caused by the electricity and consequently of its light, being carried into the body of the glass by means of the ether imbedded in, and forming a constituent part of, it. In connection with this we have to remember that the air in the tube does not glow when it is at full atmospheric pressure, but only when a certain degree of vacuum has been produced in it; and therefore it is equally obvious that it is only when the ether enclosed in the tube is reduced to the same degree of tenuity as that imbedded in the glass forming the tube, that the light of the electricity can be carried by it into the glass and make it glow. But to show this more clearly, it is necessary to refer to the steps by which we believe we have made very plain what must undoubtedly be the nature of the ether. (1) First of all we have shown that, if there be such a thing as the ether, it can be pumped out of a close vessel of any kind; which proves that it must be a material substance, and in consequence can be expanded, or rarefied, and compressed the same as any other material substance; and that if there is no such thing, something else, having these qualities, has to be invented to take its place. (2) In showing this it has been made abundantly clear by the example of the hair of a cat in variable weather, to which we may add the exhibition of lightning in daylight, that it cannot make electricity visible, or illuminate any matter, unless the quantity of electricity it has to carry bears some certain proportion to the density of the ether in the matter that is illuminated. (3) In proof of this we have shown how, through its carrying power it can convey electricity of adequate force up to very great heights, so as to illuminate very rarefied air and cause auroras; the conveying being done either directly from the earth or by means of the ether mixed with the air carried up by whirlwinds to those great heights; and (4) how electricity is carried into the body of a tube of glass and makes it glow.