112 



INIethod No. 2 depends upon tlie general form that the center of grav- 

 ity of each individual prismoid is located in from one end a distance 

 equal to 



A 



X =1 ; 



A' A + A' 

 That is to say. it is located inversely proportional to the end areas, and 



SMoments 

 Haul — 



SVolumes. 



It gi\es results always in favor of the contractor and on very short 

 hauls is rarely in error to exceed say 3.0 per cent, and on long hauls rarely 

 if every exceeds 0.5 per cent. 



Method No. ;'. depends upon the general proposition that the position 

 of half mass ]ioint is approximately the position of the center of mass 

 and graphically looks like ligure helow. 



Haul equals the mean length of the two sides of the given tropezoid 

 and the pay haul equals the aera of the tropezoid. This method gives re- 

 sults always in favor of the contractor and on very short hauls is rarely 

 in error to exceed say 4.0 per cent., and on long hauls rarely in error to 

 exceed say 6.0 per cent. 



Method No. 4, the last one treated in this report, depends for its re- 

 sults upon the area of the mass diagram. 



