[44] Whalley, in his note upon this chapter, seems to have been surprised that no mention is made here by Ptolemy of the _conjunction_; but he overlooked the fact that the chapter treats only of parts of the zodiac configurated _with each other_; and that it was not possible for Ptolemy to conceive how any part could be configurated _with itself_. It is, therefore, by no means wonderful that the conjunction is not inserted here along with the rest of the aspects; although it is frequently adverted to in subsequent chapters, and its efficacy particularly described. Of these configurations, the trine and the sextile are each called harmonious, because they are constituted between signs of the same kind; being formed between either all feminine or all masculine signs. The opposition and quartile are considered to be discordant, because they are configurations made between signs not of the same kind, but of different natures and sexes.[45] [45] From the tenor of this chapter it was formerly doubted whether the author intended to admit in his theory only zodiacal aspects, and to reject those which are called mundane; but Placidus has referred to the 4th Chapter of the 8th Book of the Almagest (which will be found in the Appendix to this translation) to prove that Ptolemy distinctly taught two kinds of aspect; one in the zodiac and one in the world. Whalley quotes the opinion of Placidus, which he says is farther confirmed by the 12th Chapter of the 3rd Book of this very treatise, where it is stated that the ascendant and the eleventh house are in sextile to each other; the ascendant and the mid-heaven in quartile; the ascendant and the ninth house in trine; and the ascendant and the occidental angle in opposition; all which certainly seems to be applicable to mundane aspects in particular. CHAPTER XVII SIGNS COMMANDING AND OBEYING Any two signs configurated with each other at an equal distance from the same, or from either equinoctial point, are termed commanding and obeying, because the ascensional and descensional times of the one are equal to those of the other, and both describe equal parallels. The signs in the summer semicircle are commanding; those in the winter semicircle, obeying: for, when the Sun is present in the former, he makes the day longer than the night; and, when in the latter, he produces the contrary effect. CHAPTER XVIII SIGNS BEHOLDING EACH OTHER, AND OF EQUAL POWER Any two signs, equally distant from either tropical sign, are equal to each other in power; because the Sun, when present in one, makes day and night, and the divisions of time, respectively equal in duration to those which he produces when present in the other. Such signs are also said to behold each other, as well for the foregoing reasons, as because each of them rises from one and the same part of the horizon, and sets in one and the same part.[46]