CONTENTS xvii 



CHAP. PAGE 



XIII. Aristotle and Theophrastus take evaporation to be the cause. 

 Strato, much in the same way, thinks that differences of internal 

 temperature are the cause ....... 240 



XIV. By some it is thought that air is the cause, but that its operation, 

 along with water, is like that of blood and air in the vessels of 

 the body. The earth, it is assumed in this case, admits air, 

 which must find an exit. When it does so violently, the result 



is an earthquake ......... 242 



XV. The earth is porous, perforated at many points, and it is thus 



that the air enters ......... 243 



XVI. The earth is full of air, nourishing plants rooted in it, and exhaling 

 enough to feed the sun and the other heavenly bodies. Air 

 is the most movable of elements ; therefore the earth, if it is 



full of air, must also have frequent movements .... 244 



XVII. Obstruction of air, just as of water, causes greater impetuosity 

 when it escapes. Wind is frequently associated with earthquakes, 



as at Chalcis ......... 245 



XVIII. Additional considerations to prove that the great cause of 

 earthquakes is air, i.e. wind ....... 247 



XIX. Metrodorus of Chios compares the rumbling of an earthquake 

 to the resonance of the voice in a tub ; the underground caves 

 impart the sound ......... 248 



XX. Various combinations of water and air supposed by Democritus 



and Epicurus to co-operate to the production of earthquakes . 249 



XXI. Air must be the cause. Different kinds of earthquakes . . 251 



XXII. First species shaking of the earth : its causes . . . 252 



XXIII. Next comes the form of concussion caused by air. The great 

 Callisthenes, who braved the fury of Alexander and lost his life 

 for it, supports this view. Submarine effects of it are particu 

 larly noticeable . . . . . . . . .253 



XXIV. Different explanations may be given of the exact method in 

 which air acts . . . . . . . . .255 



XXV. The striving of the air in subterranean caverns produces a con 

 cussion or collapse in the earth above. The area of disturbance 

 is limited, never over 200 miles, as numerous instances prove. 



The Peneiis and Ladon were thus produced .... 256 



XXVI. The nature of the soil composed of muddy accretions without 

 interstices is said to account for the exemption of Egypt from 

 earthquakes. So Delos in the sea has porous rocks which emit 

 the air easily. But the facts are wrong. There is abundant 

 proof that proximity to the sea is no safeguard against shock . 258 



XXVII. A peculiarity of the Campanian earthquake, that it killed 600 

 sheep, is explained by the emission of pestilential vapour, by 

 which sheep, with their heads close to the ground, naturally were 



most readily affected ........ 259 



XXVIII. Noxious vapours are not, however, peculiar to earthquakes. 

 They are found in several parts of Italy habitually. Such, too, 



-is the origin of new diseases . . . . . . .261 



XXIX. Excessive fear drives people mad. Earthquakes split statues 



and divide kingdoms, e.g. Sicily from Italy, Spain from Africa . 262 



