416 THE EQUILIBRIUM OF THE CIRCULAR-ARC BOW-GIRDER. 
§ 10. CoNcLUSIONS. 
The results of the investigation render it possible to design a bow-girder with 
as economical a distribution of material as in the ordinary straight encastré girder, 
and, if advantage be taken of the quantitative data calculated and plotted in figs. 5 to 9, 
with little more trouble. 
The greatest drawback to the use of the bow-girder for large spans lies in the fact 
that the distribution of stresses is affected by any uneven settlement of the supports, and 
that whereas in the straight encastré girder this dithiculty may be obviated by building 
the girder on the cantilever principle with pin-joints at the points of zero bending 
moment, in the bow-girder such points are also the points at which the twisting 
moment is approximately greatest, as will appear from a consideration of figs. 8 and 9. 
Still, as this maximum twisting moment is only about one-ninth of the maximum 
bending moment, probably the difficulty of designing a joint to take care of this torque 
would not be insuperable, and, if so, this type of design would possess many advantages. 
The great reduction in stresses which is rendered possible by the insertion of one 
or more intermediate supports forms the most powerful advocate for their use wherever 
they are not precluded by other considerations. 
University COLLEGE, 
DUNDEE. 
