xiv PHYSICAL SCIENCE 



CHAP. PAGE 



however, think too much of himself because he is governor of that 

 historic province Sicily, which has ere now decided the fate of 

 generals and of empires . . . . . . . .159 



I. Leaving Sicily and its marvels let us deal with the omitted part of 



the last book, the Nile. There is no real analogy between it and 



the Danube .......... 166 



II. The course of the Nile ; its cataracts. The inundation of the 



river. Its meaning to Egypt. Its denizens ; crocodiles and 

 dolphins in conflict. Causes of the overflow : melting of 



snow ; Etesian Winds ; drying up of the springs through internal 

 heat of the earth in winter ; the attraction of the sun in Africa 

 draws water from the sea to fill up the gap caused by evaporation 

 [none of the accounts apparently accepted] . . . .167 



III. Origin of hail; why it differs from snow . . . . .177 



IV. Causes of snow in winter, hail in spring . . . . -179 



V. It is said that the cooler air of the North (Scythia, etc.) is stirred 



by the melting of the snow in spring and floats South, causing hail 

 instead of rain . . . . . . . . .180 



VI. Hail, it is again alleged, is averted by sacrifice. If there is not a 

 victim handy you have merely to prick your finger ! . . . 181 



VII. This belief in the power of blood was an ancient superstition . 182 



VIII. Three causes why the air near the earth is warmest, and there 

 fore produces snow rather than hail . . . . . . j 82 



IX. Democritus view dense bodies are heated most quickly, and 

 retain their heat longest . . . . . . . .183 



X. The air nearest the earth is denser than elsewhere . . ,184 



XL The tops of mountains, it is urged, should be warmer because 

 nearer the sun. The difference is wholly inappreciable if we 

 adopt the scale of the universe, the true one . . . .184 



XII. The comparatively mild air near the earth causes snow, but not 



hail !86 



XIII. The despicable luxury of the effeminate Romans, who bought 

 snow, bathed in it, and must resort even to ice to cool the 

 unnatural feverish thirst born of their indulgence . . .186 



BOOK V 



TREATING OF WINDS AND MOVEMENT OF THE 

 ATMOSPHERE 



I. DEFINITION of wind air flowing in one direction. The air, like 



the sea, is always moving, even when it is thought to be still ; 

 hence the necessity of the additional qualification in one direction 193 



II. Democritus says wind arises from a multitude of atoms in a small 



space striving to get free, just like a crowd jostling each other . 194 



