What is "crystalline heavens"

Crystalline \Crys"tal*line\ (kr?s"tal-l?n or -l?n; 277), a. [L. crystallinus, from Gr. ????: cf. F. cristallin. See Crystal.]

1. Consisting, or made, of crystal.

   Mount, eagle, to my palace crystalline.
   --Shak.

2. Formed by crystallization; like crystal in texture.

   Their crystalline structure.
   --Whewell.

3. Imperfectly crystallized; as, granite is only crystalline, while quartz crystal is perfectly crystallized.

4. Fig.: Resembling crystal; pure; transparent; pellucid. ``The crystalline sky.''
   --Milton.

   Crystalline heavens, or Crystalline spheres, in the Ptolemaic system of astronomy, two transparent spheres imagined to exist between the region of the fixed stars and the primum mobile (or outer circle of the heavens, which by its motion was supposed to carry round all those within it), in order to explain certain movements of the heavenly bodies.

   Crystalline lens (Anat.), the capsular lenslike body in the eye, serving to focus the rays of light. It consists of rodlike cells derived from the external embryonic epithelium.