Elastic Equilibrium of Semi-Infinite Solid. 



43 



z- 





Fie. 6. 



Î1 = 





Thus the déviation of tlic directiou of gravity at any point can 

 be calcnlate«! with any aceni-acy. 



In the next diagram the aj^p-roxiinate eour^^e of aa-{y.co^—rj^ 

 is exhibited as a function of the distance of the point of observation 

 from the centre of the loaded circle, the radius of which is taken as 

 unity. 



§34. If we liken tlie North Atlantic to a circular basin of a 

 large radius and determine the I'elative ]iosition of Potsdam or 

 Chicago referring to the centre of it. the attraction effect of the 

 periodic fiUing and emptying of tide, which might assist in 

 producing the extra east-west force in observations of the lunar 



