A\i-. 91 



ns (5) may by suitable tra nit formations be 

 reduced to tho ordinary symmetrical equations to a straight 

 \Ve hare 



l.V 1C 



+ ('S r- ysz) JP - (j/ : 



tlu-rri'..iv 



('7P - J/2 .Y + /, v )) v r _ y j^ . / : 





n 



* ) 



ice we conclude that the equations (5) may be written 



*-) 



we see that the straight line determined bv ( 

 parallel to the direction of 11. Hence this straight line has 



llowing properties r at every mint of it the value 

 principal moment it the tame, and it lett than it it f 



not in the line ; alto for every point in the line the petition 

 of the axis of principal moment it the tame, being the line ittelf. 



line is called the central <t 



We have supposed in the investigation that R is not icro. 

 be zero we have for every origin 



Z,'-Z, JT-IT, JIT. 

 Q*-L* + M* + 



The equation (2) of Art 93 may be written 



2y + \ 



IT" 4 "' /; ' 



