364 



AREAS OF ELEVATION. 



CHAPTER continents both of America and Asia. Tlie results of 

 ^^^"^- one branch of Humboldt's elaborate investif^ations are 

 summed up in the following comparative statement of 

 all the observed areas of the Old and New World : — 



Mean 

 Leiglits. 



North America, 

 South America, 

 All America, 

 Asia, 

 Europe, 



Area in Square 

 Marine Leagues. 



607,000 



571,000 



1,178,000 



1,34G,000 



304,000 



Mean height of tlie centre 

 of grarity in English feet 



750 

 1132 



934 

 1152 



672 



Mean depth 

 of sea. 



Cnncluslnns 

 ot Laplace. 



Extent of 



eiTor. 



Laplace had drawn the conclusion from his more 

 limited opportunities of observation and comparison, 

 that the mean depth of the sea nearly corresponded 

 with the mean height of continents and islands above 

 its level. Following out a naturally assumed analogy, 

 he &ho concluded that there must be great cavities 

 in the sea, corresponding to the lofty mountains on 

 the surface of the earth ; though, at the same time, 

 he conceived that, owing to the constant depositions 

 of rivers, the denudations of currents, and the shift- 

 ing of sands, as well as the accumulation of the exu- 

 vial of marine animals, it seemed likely the original 

 extreme depth of such cavities would be considerably 

 decreased. It will be seen, however, that the investiga- 

 tions of IIuml)oldt have led to very different conclu- 

 sions. According to Laplace, the mean height of the 

 continental regions of our globe above the level of the 

 sea, should be found to be 3284 feet, whereas Humboldt 

 assigns satisfactory reasons for concluding that it cannot 

 greatly exceed 1020. Not only does this conclusion 

 show Laplace's results to have been considerably up- 

 wards of two-thirds in excess of the true phenomena of 

 relative elevation, but it still more remarkably disagrees 

 with his ideas as to the true arrangement and compara- 

 tive deptbs of tbe bed of the ocean. Numerous import- 

 ant observations have been made of late years by able 



