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148 to which much difference of opinion existed. Some of the most important things, however, were the directions. So-called circles of position were drawn through the north and south points of the horizon and any two points of the zodiac, called the significator and the promissor (the sun, moon, or planets, according as they had to be considered), and the arc of the equator included between these circles was their directio. Thus Tycho computes the direction of the ascendant to the planets (remarking that an error of four minutes in the stated time of birth will alter these directions by one degree, which corresponds to an error of one year in the time of any event foretold by a direction), and also the directions of sun, moon, and Venus to the other planets. There were various methods of "directing" or referring the effects of the planets, as they might be placed at any subsequent time, to their positions at the moment of birth. Thus Kepler says that if the sun at this moment be in a certain place in the zodiac, and a planet afterwards comes to an important place, it should be computed how many days after the birth the sun took to reach that place, and the number of days corresponds to the number of years which will elapse from the birth before the power of that configuration will be felt.

The action of each planet was very different according to the house and sign of the zodiac which it occupied. The sun and moon had each a sign (by some also called house) specially belonging to it (Leo and Cancer), and the other planets had each two, and a planet exercised the greatest power when it was in its own house. The sun and moon are the most powerful, while the others have the greater effect the nearer they are to one of those. If a planet is