150 LECTURE ON BRIDGES — BEAMS. 



direct tensile strain, or acts as a chain, need not be cellular ; and, in a 

 later example, by the same engineer — the Victoria bridge over the St. 

 Lawrence river — the bottom is composed of plates riveted closely upon 

 each other without cells, and the cells of the top are replaced by ver- 

 tical fins, which serve the same purpose. 



In the Britannia beam the sides are quite thin, serving only to con- 

 nect the upper and lower flanges, and they are stiffened by fins of T 

 iron riveted vertically over the joints. Near the ends of the beam the 

 sides are additionally strengthened to provide against the shearing 

 strain. 



To avoid change of figure laterally by the action of the wind, tri- 

 angular plates are fixed at the top and bottom, as shown in the figure. 

 Further details in regard to this beam, and the description of the man- 

 ner of raising it, will be given in the next lecture. 



[The remainder of the lectures of this course will be given in th« 

 appendix to the next annual report.] 



