124 cosmos. 



theory, the moon is a body conglomerated (like hail) by the 

 action of fire, and receives its light from the sun. The original 



saub. The opinion that the idea of the crystalline heavens being a gla- 

 cial vault (aiir glaciatus of Lactantius) arose among the ancients, from 

 their knowledge of the decrease of temperature, with the increase of 

 height in the strata of the atmosphere, as ascertained from ascending 

 great heights and from the aspect of snow-covered mountains, is refuted 

 by the circumstance that they regarded the fiery ether as lying beyond 

 the confines of the actual atmosphere, and the stars as warm bodies. 

 (Aristot., Meteor., 1, 3 ; De Cmlo, 11, 7, p. 289.) In speaking of the 

 music of the spheres (Aristot., De Ccelo, 11, p. 290), which, according 

 to the views of the Pythagoreans, is not perceived by men, because it 

 is continuous, whereas tones can only be heard when they are inter- 

 rupted by silence, Aristotle singularly enough maintains that the move- 

 ment of the spheres generates heat iu the air below them, while they 

 are themselves not heated. Their vibrations produce heat, but no sound. 

 " The motion of the sphere of the fixed stars is the most rapid (Aristdt., 

 De Cmlo, ii., 10, p. 291) ; as ths sphere and the bodies attached to it are 

 impelled in a circle, the subjacent space is heated by this movement, 

 and hence heat is diffused to the surface of the earth." (Meleorol., 1, 3, 

 p. 340.) It has always struck me as a circumstance worthy of remark, 

 that the Stagirite should constantly avoid the word crystal heaven ; for 

 the expression, " riveted stars" (ivdede/xeva aarpa), which he uses, in- 

 dicates a general idea of solid spheres, without, however, specifying the 

 nature of the substance. We do not meet with any allusion to the sub- 

 ject in Cicero, but we find in his commentator, Macrobius (Cic. Som- 

 nium Scipionis, 1, c. 20, p. 99, ed. Bip.), traces of freer ideas on the dim- 

 inution of temperature with the increase of height. According to him, 

 eternal cold prevails in the outermost zones of heaven. " Ita enim iioe 

 solum terrain sed ipsum quoque ccelum, quod vere mundus vocatur, 

 temperari a sole certissimum est, ut extremitates ejus, qua? via solis 

 longissime recesserunt, omni careant beneficio caloris, et una frigoris 

 perpetuitate torpescant." " For as it is most certain that not only the 

 earth, but the heavens themselves, which are truly called the universe, 

 are rendered more temperate by the sun, so also their confines, which 

 are most distant from the sun, are deprived of the benefits of heat, and 

 languish in a state of perpetual cold." These confines of heaven (ex- 

 tremitates cce.li), in which the Bishop of Hippo (Augustinus, ed. Antv., 

 1700, i., p. 102, and iii., p. 99) placed a region of icy-cold water near 

 Saturn the highest, and therefore the coldest, of all the planets, are 

 within the actual atmosphere, for beyond the outer limits of this space 

 lies, according to a somewhat earlier expression of Macrobius (1, c. 19, 

 p. 93), the fiery ether which enigmatically enough does not prevent this 

 eternal cold : " Stellae supra ccelum locatas, in ipso purissimo sethere sunt, 

 in quo omne quidquid est, lux naturalis et sua est, qua? tota cum igne 

 suo ita sphserae solis incumbit, ut cceli zonae, quae procul a sole sunt, 

 perpetuo frigore oppressae sint." " The stars above the heavens are 

 situated in the pure ether, in which all things, whatever they may be, 

 have a natural and proper light of their own" (the region of self-lumin- 

 ous stars), " which so impends over the sphere of the sun with all its 

 fire, that those zones of heaven which are far from the sun are oppress- 

 ed by perpetual cold." My reason for entering so circumstantially into 

 the physical and meteorological ideas of the Greeks and Romans is sim- 

 ply because these subjects, except in the works of Ukert, Henri Martin, 



