354 



On the Attraction of Ellipsoids. 



elementary pyramids with a common vertex C, Let CP be one 

 of these elementary pyramids, whose solid angle is w ; let PQ, 

 be drawn perpendicular to CO' ; from the centre draw a radius 



Fig. 2. 



vector OE parallel to CP, and from the extremity E let fall a 

 perpendicular ES on the axis CO'. 



Now the attraction of the elementary pyramid CP on the 

 material point ju, placed at its vertex = ^t/pw.CP ; and the com- 

 ponent of this attraction in the direction of the axis is 



/U/JOO).CQ, = 2///J30). 



OE 2 cos 2 



Now suppose the radius vector OE to revolve around the axis 

 OC', then the attraction on the point C of the portion of the 

 ellipsoid bounded by the two cones of revolution, whose semi- 



