As to the _modus operandi_ of planetary influence I conceive that the brain cells are infilled with a nervous pabulum of such delicate nature as to be capable of responding to the finer etheric vibrations instituted by the planets; that the electrostatic condition of the earth’s atmosphere at the moment of birth determines the particular mode or modes of vibration to which the individual brain is syntonically responsive; and I could, did space permit, immediately adduce hundreds of instances to show that whenever the same positions or planetary aspects recur in the heavens as were in existence at the moment of a birth, the individual immediately responds to the excitation, and gives instant evidence of such excitation by actions in agreement with the nature of the planets involved. CHAPTER VI PLANETARY PERIODS, ETC. We now come to the point where it will be necessary to explain more fully the various elements with which so far the reader has only been dealing in a more or less mechanical way. It is, of course, of first importance that the student of Astrology should have a correct method, and this has been given as fully as space will permit in the preceding pages. But it is also necessary that one should know why he is doing a thing, as well as how to do it. Henry Ward Beecher once said that if a man turned soil with a spade knowing why he did it, the work was more effectively done than if he did not know. For this reason it will be convenient for the student to have a general view of the cosmical elements that he employs in his calculations and of the factors that enter into his consideration when studying a horoscope. For purposes of calculation, the astronomer regards the planets as moving around the Sun in circular orbits at a uniform rate, and the positions thus obtained are called the mean longitudes of the planets. But it is known that the orbit of a planet answers to the functions of an ellipse, of which the Sun is presumed to occupy one of the foci. Then it becomes necessary to correct the Mean Longitude of the planet by an equation which is called the Centre equation. Let us make this quite clear. The circular orbit supposed in the first instance is what may be called the Mean Orbit of the planet, as compared with its true orbit, which is elliptical. Similarly, the motion of the planet in the circular orbit is called the Mean Motion, as compared with the true motion, which is variable, being quickest at the perihelion and slowest at the aphelion. The difference between the Mean longitude and the True longitude is determined by the Anomaly, which is the distance of the planet from its Aphelion, or farthest distance from the Sun. The anomaly is thus L-A, i. e., longitude minus aphelion.