218 STRUCTURE AXD MODE OF ACTION 



the trachyte of the Euganean Hills, where rise domes of 

 granular trachyte, obsidian, and pearl-stone, masses con- 

 nected by a common origin, which break through the lower 

 cretaceous rock and nummulitic lime-stone, but have never 

 flowed in narrow streams. Similar evidences of ancient re- 

 volutions of nature are found in several parts of the main- 

 land of Greece and in Asia Minor, countries -which will 

 one day offer a rich field for geological investigation, when 

 intellectual light shall revisit the seats from which it has 

 radiated to the western world, and when oppressed humanity 

 shall no longer be subject to the barbarism of Turkish rule. 

 I recall the geographical proximity of these various phse- 

 nomena, in order to shew that the basin of the Mediterra- 

 nean, with its series of islands, might have offered to an 

 attentive observer much that has been recently discovered, 

 under various forms, in South America, Teneriffe, and the 

 Aleutian Islands near the polar circle. The objects to be 

 observed were assembled within a moderate distance; yet 

 distant voyages, and the comparison of extensive regions in 

 and out of Europe, have been required for the clear percep- 

 tion and recognition of the resemblance between volcanic 

 phsenomena and their dependence on each other. 



Our ordinary language, which often givespermanency and ap- 

 parent authority to the first-formed erroneous views of natural 

 phsenoinena, but which also often points instinctively to the 

 truth, our ordinary language, I repeat, applies the term 

 " volcanic" to all eruptions of subterranean fires or molten 

 substances ; to columns of smoke and vapour rising from 

 rocks, as at Colares after the great earthquake of Lisbon, 



