1907.1 



AND CONTRACTION OF THE EARTH. 283 



3. The distribution of volcanoes, mountains, and earthquakes 

 shows that all these phenomena depend upon the sea and water 

 generally ; wherefore the depth of earthquakes is shallow and so far 

 as is known never exceeds forty miles. 



4. The principal purpose of earthquakes is the elevation of land, 

 which has made possible the development of the higher forms of life 

 upon the earth. 



5. Plato, Aristotle, Strabo and Pliny all held that water and air 

 penetrate into the earth, through hollows, fissures and crevices, thus 

 developing vapor in the heated interior, a part of which is expelled 

 from volcanoes. And they also held that earthquakes are due to the 

 tension of elastic vapors seeking to escape and diffuse themselves 

 in the atmosphere, whether these vapors break through and form 

 eruptions, or remains hidden in the earth. 



6. The movement of streams of lava beneath the earth's crust, 

 which occurs in every world-shaking earthquake, is the modern view 

 of Plato's Pyriphlegethon. Though Aristotle and his successors 

 associated earthquakes with the sea, they do not appear to have held 

 any definite theory of the movement of the fluid beneath the earth's 

 crust. From Strabo's remarks, however, it appears probable that 

 they considered mountains to be formed by earthquakes and erup- 

 tions. 



7. Aristotle correctly associated seismic sea waves with earth- 

 quakes ; and even Homer assigned these great disturbances of the 

 sea to Poseidon's trident, which was also the means employed for 

 raising up islands from the bottom. 



8. The withdrawal of the water from the shore after an earth- 

 quake and its return as a great wave, was familiar to Aristotle, and 

 is implied in his description of the sinking of Helike in 373 B.C. 



9. This pathetic calamity was due to the subsidence of a portion 

 of the sea bottom in the gulf of Corinth, after lava had been expelled 

 from beneath it, and pushed under the mountains of Arcadia. 



10. The elevation and subsidence of the land long ago contended 

 for by Strabo is now proved to occur, and examples of this movement 

 may be cited in ancient as well as in modern times. While Strabo 

 clearly states the fact of such movement he seems to have been doubt- 

 ful of the cause. Aristotle does not give the cause of these changes, 



