The practice of observing the stars began in Egypt in the reign of Ammon (about a thousand years before the Christian era), and was spread by conquest in the reign of his successor into the other parts of Africa, Asia, and Europe; but it appears to have been taught in the earliest ages by oral tradition only, for there is no good evidence of its having been reduced to written rules before some years after the first century of the Christian era, when Claudius Ptolemy (who was born and educated in Alexandria) produced a work called _Tetra-biblos_, or _Quadripartite_, being four books of the influences of the stars. In this treatise (translated into English by John Whalley--Professor of Astrology--in the year of 1786) Ptolemy seems to have collected all that which appeared to him of importance in the science. Another translation of the _Tetra-biblos_, rendered into English from the Greek paraphrase of that work by Proclus, was made in 1822 by J. M. Ashmand and this is, by most people, preferred to the translation made by Whalley. Somewhere between 1647 and 1657, Placidus di Titus, a Spanish monk, published a system of astrology, founded, to a great extent, upon Ptolemy's calculations. This work was printed in Latin and is called the _Primum Mobile_, or _First Mover_, and was translated by John Cooper in 1816; other translations have appeared, but his is the best among them. The planetary orbs, which the ancients recognised as having the most powerful influence, were seven in number (now known under the Latin names of the principal deities of the heathen mythology), viz.: Jupiter, Saturn, the Sun, Mercury, Venus, Mars and the Moon.