crops, mortality and epidemics, politics and war. They indicated the fate of society as a whole but not that of particular individuals. Secondly, there were nativities, maps of the sky at the moment of a person's births either made on the spot at the request of the infants' parents' or reconstructed for individuals of stature, those who could supply the details of their time of births. The horoscope at birth could subsequently be followed by 'annual revolutions', in which the astrologer calculated the individual's prospects for the coming year.
             The details of the client's nativity were also needed before he could avail himself of the astrologer's third main service, that of making elections or choosing the right moment for the right action. By comparing the relationship between the tendencies indicated by the client's horoscope with what was known about the future movement of the heavens, certain times could be identified as more favorable than others for embarking upon any potentially risky undertaking, such as going on a journey or choosing a wife. Finally there were horary questions the most controversial part of the astrologer's art, and one that had only been developed after the days of Ptolemy by the Arabs. Its optimistic assumption was that the astrologer could resolve any question put to him by considering the state of the heavens at the exact moment when it was asked.
             These four spheres of activity - general predictions, nativities, elections and horary questions - formed the sum of the astrologer's art. An individual might specialize in one rather than another but he was expected to be a master of them all. He might also possess a certain amount of medical learning. Different signs of the zodiac were thought to rule over different parts of the body, and a proper election of times had to be made for administering medicine, letting blood or carrying out surgical operations.
             The availability of English tre...