relation to the Constitution of the Earth's Crust. 23 



Suppose, then, a series of cap-sectors, each of axial angle 

 8a, but of different radii, respectively long enough to reach the 

 further edge of the plateau ; and let a triangular block be 

 cut off from these by a vertical plane through the crest of the 

 escarpment. The vertical attraction of the mass beyond the 

 vertical plane at the station will be that of the aggregate of 

 the sectors, minus that of the triangular block. There will 

 remain the attraction of the slope of the plateau to be added. 



F__- S 



N 



K 



P the station Kaliana. 

 H the commencement of the plateau. 

 HL=/i= 2-815 miles. 

 F the foot of the slope. 

 PL=«= 140 miles. 

 PF = 6=60miles. 



N R=depth of root of H L = t= 9*57 x 2*815 miles. 

 PK = &=26-621 miles. 



It will be observed that this value of k includes the height 

 of the station, 0*153 mile, and of its root, 1*468 mile. 



The diagram shows a section through Kaliana at P, taken 

 along the medial plane of the cap-sectors, and is intended to 

 be on a scale of y 1 ^ of an inch to five miles. The plateau 

 commences at H. NR is the depth of its root. PK is thick- 

 ness of the crust, including the plain on which the station 

 stands and its root. FH is the slope of the plateau. OR the 

 slope of the corresponding root. 



In calculating the attraction of the plateau and its root, we 

 may reckon the height of the plateau from the level of Ka- 

 liana, leaving out of consideration the attraction of the plain 

 on which the latter stands, which may be regarded as an 

 infinite plain extending under the plateau, and having its 

 attraction balanced by that of its own root. 



The attraction of the plateau will then be 



