From a quotation of this kind, which is from the lips of one of the keenest intellects of the present time, I think I am justified when I make the statement, that it is not conceded that Aether is matter, with all that that concession logically involves. Because, as Lord Kelvin points out, though it is admitted that Aether is matter, yet that admission is only a qualified admission, and not one which carries with it all the properties that essentially belong to matter, or an admission which includes the fact that Aether is gravitative, that is, subject to Gravitation. To be strictly logical and philosophical, in the statement that Aether is matter, it must be conceded not only that Aether is subject to such properties as elasticity, inertia, and compressibility, but that it is also gravitative or possesses weight. For either Aether is matter, or it is not matter. It cannot be both at one and the same time. Such a conception is altogether opposed to that simplicity which is the chief characteristic of Nature as pointed out by Newton. If therefore Aether be matter, then, to be strictly logical and philosophical, it must be conceded that Aether is gravitative, as well as having the other properties of matter, as elasticity and inertia, etc. Unless this is conceded, then we have the anomaly in Nature of matter, which is not matter, because it violates the very principles which above all others decide what is matter, viz., "That every particle of matter attracts every other particle," etc., that is, that it is gravitative. Thus by supposing that the Aether is matter, and yet not being gravitative, all the Rules of Philosophy are violated, as such a hypothesis is opposed to both the first and second Rules of Philosophy, and is contrary to all observation and experience. If Aether therefore be matter, as is conceded by the most advanced thinkers of the time, then it follows that the only logical and philosophical conclusion that can be arrived at is, that it is also subject to those properties which are the chief characteristics of all matter. These properties may be classified as follows: atomicity, gravitation, density, elasticity, inertia, and compressibility. ART. 43. _Aether is Universal._--Young in his first Hypothesis on the Aether medium states that, "A Luminiferous Aether pervades the Universe rare and elastic in a high degree" (_Phil. Tran._, 1802).