Hildegard’s views as to the internal structure of the terrestrial sphere are also somewhat difficult to follow. Her obscure and confused doctrine of Purgatory and Hell has puzzled other writers besides ourselves,[56] nor need we consider it here, but she held that the interior of the earth contained two vast spaces shaped like truncated cones, where punishment was meted out and whence many evil things had issue.[57] Her whole scheme presents analogies as well as contrasts to that of her kindred spirit Dante.[58] Hildegard, however, who died before the thirteenth century had dawned, presents us with a scheme far less definite and elaborated than that of her great successor, who had all the stores of the golden age of scholasticism on which to draw. In Hildegard’s first diagram of the universe, which is of the nature of an ‘optical section’, the world, the _sphaera elementorum_ of Johannes Sacro Bosco and other mediaeval writers, is diagrammatically represented as compounded of earth, air, fire, and water confusedly mixed in what her younger contemporary, Alexander of Neckam (1157-1217), calls ‘a certain concordant discord of the elements’. In the illustrations to the Wiesbaden Codex B the four elements have each a conventional method of representation, which appears again and again in the different miniatures (Fig. 2 and Plates XII and XIII). Around this world with its four elements is spread the atmosphere, the _aer lucidus_ or _alba pellis_, diagrammatically represented, like the earth which it enwraps, as circular. Through this _alba pellis_ no creature of earth can penetrate. Beyond are ranged in order four further shells or zones. Each zone contains one of the cardinal winds, and each cardinal wind is accompanied by two accessory winds, represented in the traditional fashion by the breath of supernatural beings. Of the four outer zones the first is the _aer aquosus_, also round, from which blows the east wind. In the outer part of the _aer aquosus_ float the clouds, and according as they contract or expand or are blown aside, the heavenly bodies above are revealed or concealed. Enwrapping the _aer aquosus_ is the _purus aether_, the widest of all the zones. The long axis of this, as of the remaining outer shells, is in the direction from east to west, thus determining the path of movement of the heavenly bodies. Scattered through the _purus aether_ are the constellations of the fixed stars, and arranged along the long axis are the moon and the two inner planets. From this zone blows the west wind. The position and constitution of this _purus aether_ is evidently the result of some misinterpretation of Aristotelian writings.