THE FIXED STARS. 125 



idea of transparency, congelation, and solidity would not, ac- 

 cording to the physics of the ancients,* and their ideas of the 

 solidification of fluids, have referred directly to cold and ice ; 

 but the affinity between tcpvoraXXog, itpvoc, and upvoraivu), 

 as well as this comparison with the most transparent of all 

 bodies, gave rise to the more definite assertion that the vault 

 of heaven consisted of ice or of glass. Thus we read in Lac- 

 tantius : " Coelum aerem glaciatum esse" and " vitreum cae- 

 lum." Empedocles undoubtedly did not refer to the glass of 

 the Phoenicians, but to air, which was supposed to be con- 

 densed into a transparent solid body by the action of the fiery 

 ether. In this comparison with ice (icpvOTaXXoc), the idea 

 of transparency predominated ; no reference being here made 

 to the origin of ice through cold, but simply to its conditions 

 of transparent condensation. While poets used the term 

 crystal, prose writers (as found in the note on the passage 

 cited from Achilles Tatius, the commentator of Aratus) lim- 

 ited themselves to the expression crystalline or crystal-like, 

 fcpvoraXXoeidrjc. In like manner, Trayoc (from nrj-yvvadat, 

 to become solid) signifies a piece of ice its condensation be 

 ing the sole point referred to. 



The idea of a crystalline vault of heaven was handed 

 down to the Middle Ages by the fathers of the Church, who 

 believed the firmament to consist of from seven to ten glassy 

 strata, incasing one 'another like the different coatings of an 

 onion. This supposition still keeps its ground in some of the 

 monasteries of Southern Europe, where I was greatly sur- 

 prised to hear a venerable prelate express an opinion in ref- 

 erence to the fall of aerolites at Aigle, which at that time 

 formed a subject of considerable interest, that the bodies we 

 called meteoric stones with vitrified crusts were not portions 

 of the fallen stone itself, but simply fragments of the crys- 



and the admirable fragment of the Meteorologia Veterum of Julius Ide- 

 ler, have hitherto beeu very imperfectly, and, for the most part, super 

 ficially considered. 



* The ideas that fire has the power of making rigid (Aristot., Probl., 

 xiv., 11), and that the formation of ice itself may be promoted by heat, 

 are deeply rooted in the physics of the ancients, and based on a fanci- 

 ful theory of contraries (Antiperistasis) on obscure conceptions of po- 

 larity (of exciting opposite qualities or conditions). ( Vide supra, p. 

 14, and note.) The quantity of hail produced was considered to be 

 proportional to the degree of heat of the atmospheric strata. (Aristot., 

 Meteor., i., 12.) In the winter fishery on the shores of the Euxhv*, 

 warm water was used to increase the ice formed in the neighborhoo-4 

 of an upright tube. (Alex. Aphrodis., fol. 86, and Plut., Deprimo Frig' 

 do, c. 12.) 



