NOTES 



333 



If, therefore, his friend doubts his word, he will call in Posidonius, 

 who will tell him that hail is formed from a watery cloud just 

 turned into liquid. No teacher is needed to explain why pellets 

 of hail are round, for all drops take that shape. Hail is nothing 

 else than suspended ice, and snow is suspended hoar-frost. In 

 this light vein Seneca thinks he has finished the subject and 

 might dismiss it, but he cannot resist the temptation to continue 

 the persiflage a little further. He quotes in a bantering style 

 some of the opinions of his brother Stoics, and after this long 

 preamble begins an inquiry into *:he distribution of density and 

 temperature in the atmosphere. 



It would have been interesting had he seriously and fully 

 stated what was known or surmised on this last topic, but he 

 dismisses it in three short chapters. We learn from these that 

 he regarded the air to be densest next the earth, and that as all 

 things retain heat better the denser and more compact they are, 

 so the air becomes less warm in proportion to its height (iS/j.). 1 

 The opinion of some persons, that the air on mountain summits 

 ought to be warmer because they are nearer the sun, is sagaciously 

 controverted, and the insignificance of all inequalities on the 

 surface of the earth in comparison with the distance from the 

 earth to the sun is forcibly expressed and illustrated. 



The subject of snow and hail is briefly reintroduced at the 

 end of the Book, probably for the purpose of affording a con- 

 venient introduction to the invective against luxury which fills 

 the concluding chapter. The preservation of snow in ice-houses, 

 and its use in the reparation of jaded appetites by cooling drinks, 

 calls forth a denunciation of the young rakes of his day, which 

 closes the discussion. 



BOOK V 



The movements of the atmosphere form the subject of dis- 

 cussion in this part of the treatise. In the first chapter the 

 author seeks for an exact definition of the term " Wind " (ventus\ 

 and ends by adopting one which is obviously inaccurate " wind 

 is air flowing in one direction," for as he afterwards speaks of 

 whirlwinds he was well aware that the movement may be in every 

 direction, or vorticose. Dismissing the opinion of Democritus 

 as to the origin of wind, he states that in his judgment wind may 

 arise from four different causes. First ; The earth itself breathes 

 forth a vast amount of air from its interior, where there are large 



1 This view hardly agrees with what is expressed in Book II. (60, 61), 

 but it more accurately expresses the fact. 



