140 CONTINUOUS GIRDERS. [CHAP. VHI. 



The quantities 2ft' and 2ft" being known, we can easily con- 

 struct the cross-lines. 



If we draw a line through U and V to intersections O and P, 

 we have O M = V V, P N = U U'. Therefore, A O and B P 



are equal to (>JH'-M / ) and (2ft"-M") , where M' and 



M" are the moments at the supports for a continuous girder, 

 and 2ft' SSI" those for a girder horizontally fixed at its ends. 



