and Orography of the Earth's Surface. 305 



knowledge of the approximate places of the subsidences, 

 which are never far from that of the elevations, because the 

 value of the elevations known, the length of the lines be- 

 tween the sea-level and the highest point of the vault re- 

 mains equal to the length of the lines of the subsidences in 

 the triangles. 



As many protuberances of the chains suffered diminutions, 

 we should include them in our calculations ; and should con- 

 struct the triangle by tangents to the two arches of the 

 vaults, and the lost summit would be restored approximately 

 by this construction. This method seems 

 also to give us a mean to determine in the //|Yv 

 interior of the earth the place where the ele- 1 / \ I 



vation began, because the causes of it are * ^ 



lower. It is only necessary to add to the height of the 

 highest point of the elevated vault above the sea-level, the 

 normal covering of the compact part of the earth under the 

 normal depth of the sea, and then to lengthen these lines in 

 its entire value in the interior of the earth. This way of 

 proceeding is the same, whether the elevation be a primi- 

 tive one, or may have taken place where others already 

 were formed, The normal depth of sea being necessarily a 

 value equal to the normal thickness of the last compact and 

 rigid covering of the earth's surface, and, on the other hand, 

 the elevated parts of the earth's surface having had their 

 place in the interior of the earth before this motion, we have 

 A C = G H, and CF = F G ; or, in other words, 



the depth of the cause of elevation, + = 2 



Ac +2CF. Now if Ac = 26, 000 feet, as in 

 the Himalayas, and CF = 2000 feet, we would _ 

 already have for the depth + —56,000 feet, 

 which is not far from that to which calcula- _ 

 tions on the temperature of the earth have 

 conducted M. Cordier ; at least it will be so 



when we correct the now acknowledged ' 4- 

 errors in some facts on which Cordier' s calculations rest, and 

 also take into consideration the destruction of the summit of 

 the chains. 



VOL. LV. NO. CX. — OCTOBER 1853. U 



