The earth lies concentrically with the _aer tenuis_, and its measurements are given thus: ‘In the midst of the _aer tenuis_ a globe was indicated, the circumference of which was everywhere equidistant from the _fortis et albus lucidusque aer_, and it was as far across as the depth of the space from the top of the highest circle to the extremity of the clouds, or from the extremity of the clouds to the circumference of the inner globe’[68] (Fig. 3). In her earlier work, the _Scivias_, Hildegard had not apparently realized the need of accounting for the independent movements of the planets other than the sun and moon. She had thus placed the moon and two of the moving stars in the _purus aether_, and the sun and the three remaining moving stars in the _lucidus ignis_. Since these spheres were moved by the winds, their contained planets would be subject to the same influences. In the _Liber Divinorum Operum_, however, she has come to realize how independent the movements of the planets really are, and she invokes a special cause for their vagaries. ‘I looked and behold in the outer fire (_lucidus ignis_) there appeared a circle which girt about the whole firmament from the east westward. From it a blast produced a movement from west to east in the opposite direction to the movement of the firmament. But this blast did not give forth his breath earthward as did the other winds, but instead thereof it governed the course of the planets.’[69] The source of the blast is represented in the Lucca MS. as the head of a supernatural being with a human face (Plate VIII). [Illustration: From the LUCCA MS. fo. 27 v Plate VIII. THE MACROCOSM THE MICROCOSM AND THE WINDS] [Illustration: Plate IX. From THE LUCCA MS fo. 37 r CELESTIAL INFLUENCES ON MEN ANIMALS AND PLANTS]