THE DEEP SEA AND ITS CONTENTS. 325 



land, and the area of the sea 2f times that of the land, tJie total 

 volume of the ocean-water is {2% x it,) Jt^st 36 thnes that of the land 

 above the sea-level. 



Now this disproportion appears to me to render it extremely 

 improbable tliat any such geological "see-saw" as may have pro- 

 duced successive alternations of land and water between the several 

 parts of the same continental platform can have ever produced 

 an exchange between any continental platform and an ocean-floor 

 such as was assumed by Sir Charles Lyell to have taken place 

 over and over again in geological time.* For even supposing all 

 the existing land of the globe to sink down to the sea-level, this 

 subsidence would be balanced by the elevation of only one thirty- 

 sixth part of the existing ocean-floor from its present average 

 depth to the same level. Or, again, let the great island-continent 

 of Australia (whose area is about one-seventeenth of the total 

 land-area of the globe) be supposed to subside to the depth of the 

 average sea-bed, so as to be altogether lost sight of not only by 

 the surface navigator but by the deep-sea surveyor, and a com- 

 pensatory elevation to take place in the existing land area, this, 

 if limited to an area of the size of Australia (which is about equal 

 to that of the whole of Europe), would raise it all to nearly the 

 height of Mont Blanc ; whilst, if spread over the entire land area 

 of the globe, // zvould ncai'ly double its present average elevation. 



Now we have no reason whatever to believe that vertical 

 upheavals or subsidences have ever taken place over extensive 

 areas to anything like such amounts, which have their parallels 

 only in the elevation of lofty mountain chains, or in the comple- 

 mentary formation of deep troughs now filled by sedimentary 

 deposit originating in the degradation of the neighbouring land ; 

 which local disturbances (as Professor Dana has shown) have 

 been effected by the lateral or horizontal ihxnst engendered during 

 the shrinkage of the globe in cooling. Moreover, the contours of 

 the oceanic area, so far as they have been yet determined by the 

 Challenger and other soundings, give no sanction whatever to 

 the notion of the existence of any submerged continental platform. 

 On the contrary, the Challenger observations enable it to be 

 affirmed with high probability that the islands which are met 

 * See chap. xii. of his Prittciples of Geology. 



