26 



Proceedings of the Royal Irish Academy. 



common centre of gravity, the polygon ACDEFB may be plotted, or, being 

 drawn as first described, it can be checked in this way. 



To. scale off the Maximum, of Maxima. 



Produce -EF, the oblique base of the fourth field, to meet the parabola at 

 c and d, bisect ed at the black spot, and scale off the vertieal height to the 

 parabola, which find to be 261 foot-tons ; also find the horizontal distance of 



