596 Mr. A. G. M. Michell on the Limits of 
The minimum volume of the frame is 
w/1 Ll 
Fa.5(5 +o). 
and therefore exceeds the frame of: fig.* 2, in which no 
limitation of extent was imposed, in the ratio 2a: (2+77), or 
122s. 1; 
j i 
3. (Fig. 4.) Constructions similar to that of figs. 2 & 3 
give the minimum frames for three forces, two of which are 
