176 PHYSICAL SCIENCE BK. iv 



if that were true, rivers in general would increase in 

 summer, and all wells would then have greater 

 abundance of water. Besides, it is not true that 

 there is an increase in the heat underground in 

 winter. Water and caves and wells are warm at 

 that season because they do not admit the frosty air 

 from without. Thus, they do not possess heat, they 

 merely exclude cold. For the same reason they 

 are chilly in summer, because the air heated by the 

 sun is drawn off to a distance, and does not pene 

 trate to them. 



27 The next account is that of Diogenes of Apollonia. 

 It runs thus : The sun attracts moisture ; the earth 

 drained of it replenishes its supply in part from the 

 sea, in part from other water. Now, it is impos 

 sible that one land should be dry and another over 

 flowing with moisture. The whole earth is full of 

 perforations, and there are paths of intercommunica 

 tion from part to part. From time to time the dry 

 parts draw upon the moist. Had not the earth 

 some source of supply, it would ere this have been 

 completely drained of its moisture. Well, then, the 

 sun attracts the waves. The localities most affected 



28 are the southern. 1 When the earth is parched, it 

 draws to it more moisture. Just as in a lamp the 

 oil flows to the point where it is consumed, so the 

 water inclines toward the place to which the over 

 powering heat of the burning earth draws it. But 

 where, it may be asked, is it drawn from ? Of 

 course, it must be from those northern regions of 

 eternal winter, where there is a superabundance of 



29 it. This is why a swift current sets from the Black 

 Sea toward the Lower Sea, without interruption, 

 and not, as in the case of other seas, with alternate 



1 The text is uncertain ; the general meaning is, however, plain. 



