210 DISCUSSION OF THE DESICCATION QUESTION. 



an uplifting of the Ocean-floor as would raise it above that level. Thus, 

 supposing that all the Land of the globe were to sink down to the sea-level, 

 such subsidence would be balanced (according to the current idea of com- 

 pensatory alternation) by an elevation up to that level of a portion of the 

 average Ocean-floor, amounting to no more than l-36th of its existing area. 

 On the other hand, the sinking of such an area as that of Papuo-Australia 

 (which forms about l-17th of the existing land-surface) to the depth of the 

 average ocean-floor, would require to balance it an elevation of the whole 

 remainder (13-14ths) of the existing land to iloulle its present average height 

 above the sea-level."* 



The first recognition of the grand idea of the persistence in position of 

 the areas of elevation and depression appears to be due to Dana, who, in his 

 memorable address before the American Association for the Advancement 

 of Science, delivered in 1855, thus stated his views: "This simplicity of 

 ocean boundary, of siu-face features, and of outline, accounts for the sim- 

 plicity of geological structure in North America; or we mny make the wider 

 statement, that all these qualities are some way connected with the position 

 and extent of the oceans, they seeming to point to the principle, that the 

 subsidence of the oceanic basins had determined the continental features ; 

 and that both results Avere involved in the earth's gradual refrigeration,''and 

 consequent contraction." 



In the first edition of his " Manual of Geology," published in 1863, Duna 

 made a still farther stop towards the recognition as a general idea, applicable 

 all over the world, that land and ocean have not, to anj' marked extent, 

 changed places with each other during the geological ages. The following 

 quotation will show exactly how far he progressed in this direction : " The 

 continents and oceans had their general outline or form defined in earliest 



time The oscillations, plications, and elevations alluded to began 



in the Azoic age ; hence the conclusion that the oceanic basins and conti- 

 nents were early outlined is unavoidable. The sinking of the ocean's bed 



and the rising of the continents were concurrent effects of one cause 



If then the continents were from the beginning the nearly stable areas (as 

 appears also from the absence of volcanoes from their interior, while they 

 abound in the oceans) the pressure of the subsiding oceanic portion has acted 

 against the resisting mass of the continents ; and thus the border between 



* See Dr. W. B. Carpenter, on " Lanil and Sea considered in relation to Geological Time," in Report of Uoyal 

 Institution of Great Britain, Meeting of Jan. 23, 1880. 



