To find the directions and quarters of the winds your method of procedure should be as follows. In the middle of the city place a marble amussium, la… - Vitruvius

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To find the directions and quarters of the winds your method of procedure should be as follows. In the middle of the city place a marble amussium, laying it true by the level, or else let the spot be made so true by means of rule and level that no amussium is necessary. In the very center of that spot set up a bronze gnomon or "shadow tracker." At about the fifth hour in the morning, take the end of the shadow cast by this gnomon, and mark it with a point. Then, opening your compasses to this point which marks the length of the gnomon's shadow, describe a circle from the center. In the afternoon watch the shadow of your gnomon as it lengthens, and when it once more touches the circumference of this circle and the shadow in the afternoon is equal in length to that of the morning, mark it with a point. From these two points describe with your compasses intersecting arcs and through their intersection and the centre let a line be drawn to the circumference of the circle to give us the quarters of south and north. ...and thus we have designed a figure equally apportioned among the eight winds.