"configuration of similar type to that which governed the child's formation in detail in the first place". Chapter 2 continues this theme in discussing the importance of calculating the precise degree of the ascendant at birth, the difficulty of recording local time precisely enough to establish this, and the methods available for rectification (i.e., ensuring the chart is correct). Chapter 3 describes how the analysis of the chart is divided into predictions of: essential, genetic qualities established prior to birth (such family and parental influences), those that become known at the birth (such as the sex of the child and birth defects), and those that can only be known post-natally (such as length of life, the quality of the mind, illnesses, marriage, children, and material fortunes). Ptolemy explains the order by which each theme becomes relevant, and follows this in his arrangement of topics presented in the remaining chapters of books III and IV. First he deals with the prenatal matters, covering the astrological significators of the parents in chapter 4, and siblings in chapter 5. Then he deals with the matters "directly concerned with the birth", explaining how to judge such issues as whether the child will be male or female (ch.6); whether the birth will produce twins or multiple children (ch.7); and whether it will involve physical defects or monstrous forms; if so, whether these are accompanied by mental deficiency, notability or honour (ch.8). The exploration of post-natal concerns begins in chapter 9 with a review of astrological factors that occur when children are not reared. This considers the indications of still births and babies that seem "half-dead", or those that have been left exposed (including whether there is possibility they may be taken up and live). Chapter 10 then details the techniques for establishing the length of life under normal circumstances. This is an important and lengthy passage of text, the techniques of which require precise astronomical detail and advanced knowledge of complex progressive techniques. Jim Tester has commented on how Ptolemy goes into an unusual level of detail in a responsibility that Bouché-Leclercq described as "the chief task of astrology, the operation judged most difficult by practitioners, most dangerous and damnable by its enemies". Such a prediction involves judicial skill as well as mathematical expertise since several 'destructive' periods may be identified but countered by other, protective astrological influences, resulting in periods of danger or illness