222 SEE— FURTHER RESEARCHES ON [April 24. 



have produced large disturbances of the level. The nature of earth- 

 quake movement in expelling lava from under the sea is too well 

 known to leave any doubt as to what is going on in Japan. And 

 the theory is confirmed by the fact that if Nipon and Yezo were 

 dug off and thrown into the Tuscarora Deep they would about fill 

 up that profound abyss and leave the sea of average depth. 



Now there is a certain analogy between the uplift of these 

 Japanese Islands, which are considera^Dle areas, by the Pacific, 

 and of the Plateau of Tibet by the Indian and Pacific oceans com- 

 bined. Undoubtedly the valleys of the Indus, Ganges and Brahma- 

 putra are the relics of ancient sea troughs which largely produced 

 the Himalayas and the great plateau of Tibet. How much these 

 troughs have been modified in later geological times we cannot 

 estimate ; but even now enough remains to tell the true story ot 

 Himalayan development. This is also indicated by the preservation 

 of the earthquake belt south of the Himalayas. The meaning of 

 these valleys and earthquake belts admits of no possible doubt. 

 Just as the whole island of Nipon is being raised by movements 

 from the Tuscarora Deep, so the whole of the Plateau of Tibet was 

 once raised by an Indian Deep, of which these valleys are the 

 remains. 



In the same way the Valley of the Po is the remains of the sea 

 valley which was most influential in uplifting the Swiss Alps. But 

 in the case of the Alps, Geikie has shown that there was also a sea 

 on the north, which has now quite disappeared, though traces of its 

 former existence still remain. 



§ 32. The Origin of Volcanoes and the Conditions of their Maxi- 

 mnni Dez'elopment. — It appears from the line. of proof developed in 

 this theory that volcanoes may break forth in any region near the 

 sea where there are severe earthquake disturbances, by which the 

 crust of the globe is sufficiently cracked to afford a vent for the 

 steam imprisoned beneath. Now such vents are greatly facilitated in 

 a chain such as the Aleutian Islands, in which the crumpling is 

 extreme, and the expulsion of lava from beneath the sea rapid and 

 violent. The crumpling breaks the crust along many lines, and 

 as the earthquakes due to the expulsion of lava are both frequent 

 and terrible, the chance of steam breaking through to the surface 



