xviii PHYSICAL SCIENCE 



CHAP. PAGE 



XXX. The action of the air accounts for all the detailed phenomena, 

 splitting of walls, houses, towers, statues ; also for the prolonga- 

 tion of shocks for several days . . . . . .263 



XXXI. A further proof that air is the agent is to be found in the 

 gradually diminishing violence of the successive shocks. Pheno- 

 mena in the pavement witnessed by a philosopher who was in 



his bath .......... 264 



XXXII. The moral. Life hangs on a thread ; why should one dread 

 the loss of it ? The greatness of the cause of death is no source 

 of terror. The hereafter is better and safer than earth. There 

 there is no fear of earthquake or thunderstorm, fire or flood. 

 Fear of death magnifies all human risks. Do not dread death, 



long for it, and, if necessary, meet it half way .... 265 



BOOK VII 



TREATING OF COMETS 



I. PHENOMENA, however wonderful, are not noted and admired 



unless they are uncommon. The sun and moon and starry 

 heavens have no observers, but a Comet at once sets the 

 whole world agog. The nature of the stars is a sublime and like- 

 wise a profitable study . . . . . . . .271 



II. The nature of Comets has not been hitherto fully investigated. 



They are so rare that one wants a record of the movements of all 



ever observed ......... 273 



III. Democritus, Eudoxus, Conon, Epigenes, and Apollonius of 

 Myndus all fail to give any satisfactory account of the matter. 



Nor had the Egyptians or Chaldaeans investigated them . . 274 



IV. Epigenes explains the Comet as due to a conjunction of Saturn 

 with Mars or the Sun : it is akin to whirlwind and ' ' beam " 

 meteors .......... 275 



V. But there are essential differences between whirlwind, which is 



terrestrial, and beams and torches, which are abo iT e the clouds. 

 There is a difference of duration also. Beams and Comets, it is 

 true, have been mistaken for one another. It was a Comet, 

 according to Aristotle, that appeared before the destruction of 

 Buris and Helice. The character of the flame differs in the two 

 forms ........... 276 



VI. There are two kinds of Comets, according to Epigenes. They 

 are produced by air driven up and setting on fire suitable material 

 above, which takes place every day at the same hour . . 277 



VII. But Comets are not concomitants of winds ; there is no 

 parallelism in the phenomena. The higher ones, which have an 

 orbit, he attributes to the north wind, but the facts do not square 



here either .......... 278 



VIII. The course and altitude of Comets render the whirlwind 

 explanation impossible ........ 279 



IX. The force and duration of whirlwinds are similarly inadequate . 280 



