TEKKESTEIAL PHENOMENA. 31 



friction of bodies in motion, the heavenly bodies moving in 

 their respective courses still more readily cause the ignition 

 of the air beneath them, this bemg more of the nature of 

 fire than is any solid missile. The heavenly bodies them- 

 selves are not heated. Where the Sun happens to be fixed 

 the heating effects are intense, but, in Meteorol. i. c. 3, s. 21, 

 he says that the Sun, which in an especial degree seems to 

 be hot, appears to be white and not fiery. It has been 

 stated already that he did not believe that the stars were of 

 fire, nor that they were carried round in a medium of fire. 

 He seems to have believed that they moved in contact with 

 the medium oi fire or aii' within their spheres of motion.* 



Such were Aristotle's views. They are difficult to 

 understand, not only because they are not explained 

 sufficiently fully, but also because they are based, in part at 

 least, on fanciful assumptions. It is not clear what was the 

 nature of the substance the ignition of which was caused by 

 the motion of the heavenly bodies, except that it was 

 intermediate between fire or flame and air, like one of the 

 substances which Alexander, Simplicius, Philoponus, and 

 some other ancient writers identified with Anaximander's 

 infinite or primitive matter. His assertion that the Sun 

 appears to be white and not fiery is strange, and suggests 

 that he had not seen a wliite-hot fire. It will be seen, 

 in the discussion on his views on heat phenomena, that he 

 greatly underestimated the intensity of heat of an ordinary 

 red-hot fire. Again, Aristotle does not satisfactorily explain 

 why the heating effect is so intense where the Sun happens 

 to be secured. In an attempt to explain this, in Meteorol. 

 i. c. 3, s. 20, he says that the motion of the Sun is sufficiently 

 rapid and the Sun is near enough to us, for the moving body 

 should not be too far away and its motion should be rapid, 

 for the heat to be effective. The stars, he says, certainly 

 move rapidly, but are too far away, while the Moon is nearer, 

 but her motion is slow. The statement that the heavenly 

 bodies are not heated would be difficult to understand were 

 it not for Aristotle's assumption, already referred to, that the 

 heavenly bodies are of aether, which is incapable of change. . 



According to Aristotle the stars are spherical, but they 

 neither rotate nor revolve of themselves, being secured in 

 the circles of the Heavens, which are rotating.! His opinion 

 that the stars are spherical was also held, he says, by others, t 



- De Ccelo, ii. c. 4, 287a, ii, c. 7. 289rt. 



f De Ccelo, ii, c. 8, 2896, and 290a. J De Ccelo, ii. c. 8, 290a. 



