THE FIXED STARS. 167 



from the sun. The original idea of transparency, congela- 

 tion, and solidity, would not, according to the physics of the 



Their vibrations produce heat, but no sound. " The motion 

 of the sphere of the fixed stars is the most rapid, ( Aristot. de 

 Ccelo, ii. 10, p. 291) ; as this 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." (Meteorol. 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 ex- 

 pression, "rivetted stars" (evdedep-eva aorpa), which he uses, 

 indicates a general idea of solid spheres, without, however, 

 specifying the nature of the substance. We do not meet 

 with any allusion to the subject in Cicero, but we find in his 

 Commentator Macrobius, (Cic. Somnium Scipionis, 1, c. 20, 

 p. 99, ed. Bip.) traces of freer ideas on the diminution of 

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

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

 enim non solum terrain sed ipsum quoque coelum, quod vere 

 mundus vocatur, temperari a sole certissimum est, ut extre- 

 mitates ejus, qua3 via solis longissime recesserunt, omni ca- 

 reant 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 con- 

 fines, 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 (extremitates cceli), in which 

 the Bishop of Hippo (Augustinus, ed. Antv. 1700, 1, 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 locates, in ipso purissimo eethere sunt, in quo omne 

 quidquid est, lux naturalis et sua est, quse tota cum igne suo 

 ita sphaera solis incumbit, ut co3li zona3, qua3 procul a sole 

 sunt, perpetuo frigore oppresses sint." "The stars above 

 the heavens are situated in the pure ether, in which all 



