4 M. Ami Boue Oh the Palicohydvography 



The same may be said of the southern part of the Pacific, 

 which is as large as all the continents together. On the 

 contrary, in the Northern Ocean to the 30th lat. north, the 

 sea has only a relative smaller depth, and the dry land fills 

 up there nearly as much space as the water. 



We may observe, probably, that the volcanic action may 

 modify our conclusions. We find, for instance, in Mont 

 Blanc only metamorphic rocks, and in the Himalaya, second- 

 ary slates, and the highest pinnacles of the Andes nothing 

 else than volcanic cones, so that we can only compare the 

 height of the old vaults upon which these volcanic matters 

 were united. 



Volcanic action is still an agent very little known, and its 

 force of elevation has not yet been determined. When we see 

 on certain large volcanic islands, heights like those of Mont 

 Blanc, for instance in Sicily, at TenerhTe, &c, and even still 

 higher peaks in other volcanoes, those immense accumulations 

 of igneous matters do not decide the question, if the volcanic 

 force has been able to elevate a Chimborazo at the height of 

 24,000 feet from the mentioned normal sea-depth of 1500 

 to 2000 feet. According to all our observations, it must, on 

 the contrary, be admitted, that the volcanic islands give us 

 the limits of the volcanic force of elevation, and that in other 

 places the height of the base of the volcanoes enables us to 

 judge of their extraordinary altitude. In that way we see 

 the lava flowing constantly from the crater of the Kirauea 

 volcano upon the isle of Hawaii, which is only 3800 feet in 

 height. We see volcanoes like Etna ejecting periodically 

 stones to a height of COOO feet, but the lava flows only 

 through rents in the sides of the cones far below the high 

 summits. In the Andes, whose trachytic domes predomi- 

 nate, the eruptions are also below, and the ashes and smoke 

 go out above. This position of the volcanoes of South 

 America upon the earth's vaults, may possibly explain how 

 the volcanic phenomena and earthquakes in those countries 

 are much stronger than elsewhere, because the action takes 

 place under a covering filled with more rents, and more easy 

 to be moved, being already bent to a vault. Generally, 

 the higher the volcano, it is the more easily moved ; on the 



