70 CAUSES OF GEOLOGICAL CHANGES. 
1. The cause of the activity of volcanoes, whatever may be 
its nature, is extensively distributed through the crust of the 
globe, since there is no part of it of considerable extent in 
which they do not occur. 
They are more frequently upon islands than on the continent. 
Iceland, in the northern Atlantic, has a number of active volca- 
noes — ten or twelve. Sicily, on the south of Europe, has iEtna, 
and the kingdom of Naples, Vesuvius. The islands north of Si- 
cily and also the southern islands of the Grecian Archipelago, are 
volcanic. Morier says, that several mountains in Persia constantly 
emit smoke. Humboldt supposes himself to have ascertained the 
existence of a volcanic district in central Tartary. The peninsula 
of Kamschatka appears to be in a great part the product of volca- 
nic eruptions, and contains a number of active volcanoes, some of 
them of immense size. The long chain of islands extending from 
Kamschatka to New Holland, is of a similar character. The 
Kurile Isles appear to consist of a train of volcanic mountains, of 
which many are still subject to eruption The Japanese islands 
contain ten occasionally active vents. The Polynesian Archi- 
pelago owes its existence, to a great extent, to volcanic action. 
The Philippine Islands, the Moluccas, Celebes, Java, Sumatra, 
New Guinea, the Marianne Isles, one or two of the Friendly Is- 
lands, and the Sandwich Islands, may be mentioned especially as 
the seats of volcanic fires. 
Very little is known of the interior of Africa, but most of the 
islands by which it is surrounded are volcanic. Except on the 
coast of Greenland, there are no active volcanoes on the eastern 
side of North America, but they are not wanting on the western 
side. Capt. Cook saw a volcano in lat. 61°, and two others of 
immense size a little farther south. These belong to the system 
extending from Kamschatka along the eastern side of Asia. Five 
are reported to exist in California. Mexico has five. Three of 
the West India Islands (St. Vincent, St. Lucia, and Guadaloupe), 
are active volcanoes; and the long chain of the gigantic Andes 
would seem to be almost one continued volcano, so numerous are 
the volcanic peaks. These statements will be sufficient to show 
the extent to which the causes of the activity of volcanoes are 
distributed through the crust of the globe. 
2. When these fires have once been kindled in the interior 
of the earth, they continue to burn for ages, thereby affording 
evidence that in the particular localities where they exist, the 
causes of their activity are accumulated, to an immense extent. 
The magazine from which iEtna has been supplied for more 
than two thousand years, is not yet exhausted, and what amount 
of material that vast furnace is capable of consuming in a single 
day, (if, as has been supposed, its eruptions are the effect of a 
real combustion j he will best judge who has been upon the spot, 
measured with his eye the height of the mountain and the capacity 
of the crater, and recollected that the latter lias sometimes been 
