54 THE POPULAR SCIENCE MONTHLY. 



the year 79. If wo include only habitual vents of considerable impor- 

 tance, which we have reason to believe may still be in active con- 

 dition, the number may be put at between three hundred and three 

 hundred and fifty. Most of these are marked by more or less consid- 

 erable mountains formed of the matters ejected from them. If we 

 include the mountains which exhibit the main features of volcanoes, 

 but concerning the activity of which we have no record or tradition, 

 the number will not fall much short of one thousand. Then there are 

 other "ruined volcanoes," the cones of which have been worn away 

 and of which the " ground-plans " only are left, still more numerous. 

 The smaller temporary openings, usually subordinate to the habitual 

 vents, known to ancient and modern history and tradition, may be 

 counted by thousands and tens of thousands. The still feebler mani- 

 festations steam-jets, geysers, thermal and mineral waters, fumaroles, 

 mud-volcanoes, and the like must be numbered by millions. The 

 latter class seem to play a small part as we contemplate them singly, 

 but their force in the aggregate probably far exceeds that of all the 

 great habitual vents. These volcanoes, in all their classes, are very 

 unequally distributed over the globe. Vesuvius is the only habitual 

 vent on the Continent of Europe, and it is on the shores of the Medi- 

 terranean ; the Mediterranean islands contain six ; Africa has ten 

 four on the western, six on the eastern coast ; Asia, so far as is 

 known, twenty-four, twelve of which are on the peninsula of Kamt- 

 chatka. None are known in Australia. North America has twenty 

 volcanoes, Central America twenty-five, and South America thirty- 

 seven. In all, one hundred and seventeen volcanoes are situated on 

 the great continental lands, leaving nearly twice that number distrib- 

 uted over the islands of the oceans. 



In nearly all cases, the volcanoes are either close to the shores of 

 the continent or at no very great distance from them. The only 

 known exceptions are in the Central Asian plateau and Chinese Man- 

 tchooria, concerning which more accurate information is needed. All 

 the oceanic islands that are not coral reefs are of volcanic origin, and 

 many of them contain active volcanoes. A ridge running through the 

 midst of the Atlantic Ocean and embracing the Islands of Jan Mayen, 

 Iceland, the Azores, Canaries, and "West Indies, contains forty active 

 volcanoes and a greater number of extinct ones. A similar line in 

 the Pacific Ocean, including the group of islands southeast of the 

 Asiatic Continent, "the grandest focus of volcanic activity on the 

 globe," contains no less than one hundred and fifty active volcanoes ; 

 and, if we include those on lines branching from the main one, half 

 the habitually active vents of the globe. A third series of volcanoes 

 starts from near the last one in the neighborhood of Behring Strait, 

 and stretches along the whole western coast of the American Conti- 

 nent, with about eighty active vents. 



The volcanoes of the globe thus usually assume a linear arrange- 



