1 32 Volcanos. 



basalt, alternating repeatedly with compact limestone strata. 

 The hills of the Phlegraean fields near Naples the author sup- 

 poses to have been thrown up by subaqueous eruptions from a 

 very shallow shore, which has been subsequently elevated above 

 the sea-level, by subterranean expansion. 



u When the summit of a submarine volcano is raised above 

 the surface of the sea, it conforms to all the laws, already 

 investigated, which regulate the conduct of a subaerial vent. 

 Its elevation takes place in one or both of two modes, viz. 

 1. By the accumulation of matter, protruded by repeated 

 eruptions. 2. By elevation, en masse, from the expansion of the 

 inferior lava. The latter mode will be often accompanied by 

 the heaving up of more or less extensive masses of the neigh- 

 boring strata. Examples are given of volcanic islands, which 

 appear to owe their elevation from the depth of the sea to 

 these different processes. Iceland, Teneriffe, Sicily, and some 

 of the Leeward Isles, are quoted as islands which have risen 

 by the joint effect of both the above modes of subterranean ac- 

 tivity ; the Isle of France, Pulo Nias, some of the Madeiras, and of 

 the Hebrides, as instances of the latter mode acting alone. The 

 author supposes the coralline islands of the Pacific to be mostly 

 based upon volcanic submarine eminences ; their circular or ellip- 

 tical figure corresponding to the ridge of the central crater of 

 a volcano. Many have been subsequently raised far above the 

 level of the ocean ; and the earthquakes, to which they are so 

 often liable, prove their elevation to be owing to subterranean in- 

 tumesence, and to be still in progress, while the continual growth 

 of fresh coral on their shores, augments at the same time their 

 horizontal extent. 



" Chapter IX treats of Volcanic Systems. 



'" The volcanic vents observable on the surface of the globe, 

 are arranged either in detached groups, as those of Iceland, 

 the Azores, Canaries, Cape Verd Isles, &c; or, and this is 

 the prevailing case, in linear trains, at a greater or less distance ; 

 often so close, that the products of the neighboring volcanos 

 are in contact, and produce strings of volcanic mountains, such 

 as occur in France, Germany, the Leeward Isles, Java, Su- 

 matra, Japan, Kamschatka, &c. The most remarkable series 

 of vents of this kind on the globe, is that prodigous train which, 

 beginning in the Andaman and Nicobar Isles, runs through Su- 

 matra, Java, Sumbawa, Sumba, Timor, and the whole group 

 of the Moluccas, whence taking a northerly direction, it has 

 produced the Phillippines and Loochoo Isles, Japan, Jesso, the 

 Kurile group, and the peninsula of Kamschatka. Thence it 

 diverges to the east, forming the chain of the Aleutian Isles, 

 and appears to be continued southerly along the western coast of 



