336 Attempt to determine the mean height of Continents. 



Europe, 106 toises (205 metres). 



North America, 117 ... (228 ... ). 

 South America, 177 ... (345 ... ). 

 Asia, 180 ... C351 ... ). 



For the whole of the new continent we liave 146 toises 

 (285 metres), and for the height of the centre of gravity of the 

 vohxme of all the continental masses (Africa excepted) above 

 the level of the present seas, 157.8 toises or 307 metres. 



Von Hoff, who has measm*ed with extreme accuracy 1076 

 diflFerent points, the greater part of them in the mountainous 

 portion of Thuringia, over an extent of 224 square geographical 

 miles, estimates that there are about five heights for each 

 square mile, but that these heights are unequally scattered. 

 M. de Humboldt has asked Von HofF, always for the purpose 

 of verifying Laplace's hypothesis respecting the mass of con- 

 tinents, to calculate the mean height of the hypsometrical 

 measurements which he has made. This philosopher has found 

 it to be 166 toises, that is to say, 8 toises more than the result 

 at which M. de Humboldt had arrived. We ought theiice to 

 conclude, that, since a very mountainous country of Thuringia 

 was measured, the number, 157 toises, or 942 feet, is a limit 

 rather too high than too low. 



In the certainty in which we now are respecting the. pro- 

 gressive and partial rising of Sweden (one of the most im- 

 portant facts in physical geography, for a knowledge of which 

 we are indebted to M. de Buch), we may suppose that the 

 centre of gravity will not always continue the same. At the 

 same time, considering the smallness of the masses which are 

 raised and the weakness of the subterranean forces in action, 

 it may be presumed, regarding such variations, that they will 

 in a great measure compensate each other, and that the posi- 

 tion of the centre of gravity above the ocean will not be much 

 changed ; but a new circumstance, which appears to result 

 from the numerical calculations of this hypsometrical labour, 

 is, that the smallest heights in our hemisphere belong to the 

 continental masses of the north. Thus Europe has furnished 

 105 toises. North America 117 toises. The prominent cha- 

 racter of Asia between 28° and 40" of latitude compensates 

 the subtractive effect of the lower portions of Siberia. Asia 



