,907.1 AND CONTRACTION OF THE EARTH. 269 



philosophical and accordant with Newton's rule this is than the 

 singular modern method of dividing earthquakes into two separate 

 classes, volcanic and tectonic ! 



Aristotle holds not only that earthquakes are due to vapor in 

 the earth, but also that they are most prevalent near the sea. In 

 other parts of the ''Meteorology" (Lib. i, Cap. iv.), he says that 

 the '' distribution of land and sea in particular regions does not 

 endure throughout all time, but it becomes sea in those parts where 

 it was land, and again it becomes land where it was sea " ; and finally 

 adds " everything changes in the course of time." Aristotle also 

 correctly associated seismic sea waves with earthquakes, and points 

 out cases of islands and volcanoes upheaved in the sea. The philo- 

 sophical position which he occupied was thus extraordinarily ad- 

 vanced, and there is little wonder that his views were adopted and 

 elaborated by Strabo and Pliny. This simple and orderly develop- 

 ment of thought among the ancients is in melancholy contrast to 

 the disconnected and anachronous views still prevalent on these 

 subjects in our own time. 

 § 23. Explanation of the Sinking of Helike and destruction of Biira, 



373 B.C. 



We have seen that Strabo says that Helike sank in the night,^ 

 after the region had been shaken by a great earthquake. He says 

 Helike was 12 stadia from the sea, and Bura 40 stadia, about 

 1.5 and 5 miles respectively. In his large work on the "Face of 

 the Earth " (Vol. II., pp. 448, 464) Professor Suess explains this 

 sinking by the shaking down of an alluvial deposit, which broke 

 loose from the older formation, thus causing it to slip into the sea. 

 The process described by Suess is a familiar one where a narrow 

 band of soil is formed near steep cliffs ; but this shaking lose ob- 

 viously could not occur where the extent of the deposit is from 

 1.5 to 5 miles in width. No alluvial deposit of this width would 

 slide during an earthquake, unless it was on the slope of a com- 

 paratively steep mountain, and the strata under it were inclined at a 

 steep angle, of say 30°, which was not the case in the region of 

 Helike and Bura. These cities were both built on decidedly solid 

 lowlands along the seashore, and with such a broad base the al- 

 luvial deposits could not slide into the sea. What J. Schmidt ob- 

 ^ According to Heracleides. 



