348 SEE— THE CAUSE OF EARTHQUAKES. [October 19, 



the view now generally held that compensation is always going on, 

 through the changes of levels due to erosion and other causes. 

 Mr. Hayford's paper is extremely important in showing that the 

 depth of compensation is not great, and the principal inequalities 

 of density are essentially limited to the earth's crust, complete aver- 

 age compensation for the whole country occurring within about 

 three or four times that depth. The result, therefore, accords well 

 with the views developed in the present investigation. In his dis- 

 cussion of Hayford's paper. Major Button, who was present, re- 

 marked that " the heavy masses of sediment which are formed upon 

 the bottom of the sea can, I conceive, only be elevated by a positive 

 uplifting force." 



VII. The Origin of Islands and the Secular Movement of 



THE Strand. 



§ 30. Submarine earthquakes and volcanoes. 



The eruption of volcanoes from the sea was noted by the Greeks, 

 as we learn from Aristotle (Meteor., ii, 8, 17-19), quoted by Hum- 

 boldt in Cosmos, Vol. I, p. 240, Bohn's translation : 



"The heaving of the earth does not cease till the wind (avFfio^) which 

 occasions the shocks has made its escape into the crust of the earth. It is 

 not long ago since this actually happened at Heraclea in Pontus, and a 

 similar event formerly occurred at Hiera, one of the Aeolian Islands. A por- 

 tion of the earth swelled up, and with loud noise rose into the form of a hill, 

 till the mighty urging blast (7Tvev/na) found an outlet, and ejected sparks and 

 ashes which covered the neighborhood of Lapari, and even extended to sev- 

 eral Italian cities." 



Strabo (lib. i, p. 59) describes the flaming eruption observed at 

 Methone in the year 282 B. C, near the town in the Bay of Her- 

 mione, saying a fiery mountain arose seven stadia in height, inac- 

 cessible by day on account of its heat and sulphurous flames, but 

 emitting an agreeable odor at night. It was so hot that the sea 

 boiled for a distance of five stadia, and was turbid and filled with 

 detached masses of rock for full twenty stadia. This eruption is 

 also mentioned by Ovid^ (Metam., xv). 



^ " Near Troezen is a tumulus, steep and devoid of trees, once a plain, 

 now a mountain. The vapours enclosed in dark caverns in vain seek a pas- 

 sage by which they may escape. The heaving earth, inflated by the force 

 of the compressed vapours, expands like a bladder filled with air, or like a 

 goat skin. The ground has remained thus inflated and the high projecting 



y 



