248 SEE— TEMPERATURE, SECULAR COOLING [April 20, 



" On the other hand earthquakes are produced, and often extend over 

 but a small area ; yet the winds are not local in character ; on the contrary 

 they arise whenever the exhalations, those over the area itself, and those 

 of the neighbouring region, act in concert; just as we say the droughts are 

 produced, and the rainy seasons in turn at any given place. And the earth- 

 quakes are produced likewise in the very same manner; but it is not so for 

 the winds, for all these phenomena (the earthquakes, droughts and rains) 

 have their origin in the earth, in such a way that they work together; the 

 power of the sun, however, is not similar, but is rather exerted upon those 

 exhalations high above the earth, so that whenever they experience the in- 

 fluence of the sun's annual circuit, according to the differences of the places 

 on the earth, they all flow together. 



" Whenever there is therefore considerable exhalation it shakes the earth, 

 as in a trembling to and fro ; it occurs more rarely, and only in certain places, 

 as a pulsation, oscillating up and down; wherefore also shocks of this kind 

 are of slight intensity; for it is not easy for a body of the elements to join 

 together in this movement ; since the secretion of vapor is many times larger 

 at the surface than at great depths. Wherever such an earthquake arises, 

 there is a hurling forth of a multitude of stones, just as in the case of sand 

 winnowed by the wind. In this manner, when such an earthquake occurred, 

 ejection of stones took place in Sicily, in the region called the Phlegraean 

 fields, and in the Ligurian country. 



" And in the islands of the deep sea earthquakes occur less often than 

 in the islands near the continents. The immensity of the sea cools the 

 exhalations, and it hinders them and resists them by the weight which it 

 imposes upon them. Moreover even when the winds blow the sea always 

 oscillates, and is not shaken powerfully by the agitating blasts. 



" But on account of the enormous space it occupies it is not in it, but 

 from it that the exhalations are produced, and those from the earth follow 

 them : and the islands lying close to the mainland are only a part of the 

 mainland itself; the space between, on account of its smallness, being of no 

 importance; but those islands in the sea cannot be moved without disturbng 

 the whole sea, which is spread around them. So much therefore may be 

 said in regard to earthquakes, and their nature, and the cause through which 

 they arise, and the other most important circumstances closely associated 

 with them." 



De Mundo/ Cap. IV. 



(Scholars do not consider this work a genuine production of Aris- 

 totle, but no doubt it represents the Peripatetic School of Philo- 

 sophy.) ' 



" A blast of vapor erupting from the earth is carried upwards from the 

 depths below or from the yawning fissure; whenever it is borne with much 

 whirling movement there is a terrestrial thunderstorm; the blast of vapor 

 ascends to the clouds, dense and moist, and outwardly scatters violently the 



^irepl KOG/LLovrrpbc 'A7ie^av6pov. This must not be confused with the treatise 

 on the heavens, which is entitled ttf/k ovpavov. 



