298 SEE— TEMPERATURE, SECULAR COOLING [April 20, 



to what might have been expected from the sudden obUteration of 

 HeHke, at once the most important city in Achaia, and the center of 

 the Panionian league, owing to the prosperity and increasing prestige 

 it had enjoyed since the days of Homer. As Aristotle tries to ac- 

 count for the disaster by the theory of opposing winds, it is evident 

 that it must have been a subject of keen speculation among the lead- 

 ing Greek philosophers. Although the explanation given by Aris- 

 totle is now invalidated by the advancement of science, he was entirely 

 correct in ascribing this dreadful calamity to the agitation of vapors 

 confined within the earth, which in seeking release finally brought 

 on the cataclysm. 



There are few results in science of deeper interest than those 

 obtained by a principle which enables us to remount to the earliest 

 ages of history, and to explain phenomena contemporaneously ob- 

 served by the greatest minds of antiquity. This impressively illus- 

 trates the difference between a discovery disclosing a true physical 

 cause and an effort directed to the mere observation of phenomena. 

 A vera causa explains with equal facility the phenomena of every 

 country and the observations of every age, whereas without it we 

 can not correctly understand the commonest phenomena witnessed 

 in our own time. 



April 30, 1907. 



Final Note. 



Since the above discussion was completed, the writer has been 

 much impressed with the excellent maps of the ocean depths pub- 

 lished by the U. S. Coast and Geodetic Survey (Physical Hydrog- 

 raphy, Manual of Tides, Part IV A, by Rollin A. Harris, Appendix 

 7, Report for 1900). The reader is requested to study especially 

 maps 19 and 20, of this appendix, and to notice how the earthquake 

 belts of the world as laid down by Milne follow the deep trenches 

 in the sea. The borders of the North Pacific ocean, about Alaska, 

 the Aleutian and Kurile Islands, and Japan are literally surrounded 

 by these deep, narrow trenches, running right through the centres 

 of the great earthquake belts of the globe. As these trenches are 

 very long, narrow, and deep, and at the same time exactly paralleled 

 by chains of islands rising out of the sea, which are mountain ranges 

 under water, we see at once the true cause of earthquakes. The 



