TEREESTRIAL PHENOMENA. 43 



probable that it was hot air mingled with humic and other 

 effluvia rising from the hot earth. It may be mentioned 

 here that, in the Aristotelian work, De Mundo, c. 4, 394, it 

 is stated that wind is nothing else but a large quantity of 

 compressed air in motion. This work was not written by 

 Aristotle. 



His views on the wet or vaporous exhalation are much 

 easier to understand, and are set out at great length in 

 Meteorol. i. cc. 9-12. He probably did not know that water 

 vapour is diffused throughout the atmosphere, but he gives 

 a substantially correct explanation of the formation of rain 

 and clouds, for he says that the vapour raised by the Sun's 

 heat and by any other celestial source of heat is cooled and 

 condensed and descends to the earth, and that clouds result 

 from a separation of watery vapour from the air.* 



Dew and hoar-frost are formed from watery vapour 

 during clear, calm weather, t Hail, he says, is ice, and is 

 produced most in spring and autumn, less frequently in 

 summer, and seldom in winter.! It is formed in conse- 

 quence of a rapid freezing of water separated from the air, 

 the freezing being so rapid that the water is converted into 

 ice before it reaches the ground. § The freezing is more 

 rapid, he says, if the water is warm before freezing com- 

 mences. |1 Some examples of this, which Aristotle records, 

 will be considered in Chapter iv. Up till his own time, 

 Aristotle says, three different views about the causes of 

 earthquakes had been put forth. 1l According to him, 

 Anaxagoras believed that they were caused by the aether of 

 the upper regions bursting into the under parts and hollows of 

 the Earth.** Democritus assumed that the Earth, already 

 saturated with water and, in addition, receiving quantities of 

 rain-water, became shaken thereby.! t Anaximenes believed 

 that the Earth was shaken by masses falling in, such masses 

 having been broken away during a process of drying the 

 Earth, which he assumed to be quite moist. 1 1 



Setting forth his own views on earthquakes, Aristotle 

 says that the Earth of itself is dry, but, on account of the 

 rains, becomes moist, so that, being subjected to the action 

 of the Sun's heat and its own internal heat, a large quantity 



* Meteorol. i. c. 9, ss. 2-4. ' f Ihld. i. c. 10, s. 4. 



\ Ibid. i. c. 12, s. 1. § Ibid. i. c. 12, ss. 13 and 14. 



II Ibid. i. c. 12, s. 17. ^f Ibid. ii. c. 7, s. 1. 



** Ibid. ii. c. 7, s. 2. ft Ibid. ii. c. 7, s. 6. 



II Ibid. ii. c. 7, 6. 6. 



