REACTION OF THE INTERIOR OF THE EARTH 



8. The Pacific. 



>mpare the part of the earth's surface which 

 is at present covered by water with the area of dry land 

 (the ratio being approximately ( 506 ) as 2 '7 : 1), we may 

 be struck by surprise in geological respects at the rarity 

 of still active volcanoes in the oceanic region. The 



O 



Pacific Ocean, whose surface is nearly one sixth greater 

 than that of the whole dry land of our planet, whose 

 breadth in the equatorial region, from the Gralapagos to 

 the Pelew islands, is nearly two fifths of the whole cir- 

 cumference of the globe, presents fewer smoking vol- 

 canoes, fewer openings through which the interior of 

 the planet still maintains an active communication with 

 its atmospheric envelope, than does the single island of 

 Java. The geologist of the great American exploring 

 expedition under the command of Charles Wilkes 

 (1838-1842), the ingenious James Dana, has un- 

 doubtedly the great merit of having shed a new light 

 on the whole Pacific world of islands, by taking as a 

 foundation his own researches combined with a careful 

 assemblage and comparison of all well-assured previous 

 observations, and proceeding thence to a generalisation 

 of views repecting the shape, distribution, and direction 

 of axis in all the various groups of islands ; the charac- 

 ter of the rock ; and periods of subsidence and elevation 

 of extensive tracts of the bottom of the sea. If I avail 

 myself largely of his writings as well as of the admir- 

 able investigations of Charles Darwin, the geologist of 

 Captain Fitz-Koy's expedition in 1832-1836, without 

 special reference on each occasion, the high esteem 

 which I have for so many years expressed for both those 



