ANNUAL ADDRESS. XIII, 
per foot run per track, covering all tracks from tower to tower at 
rest or moving slowly. Trains 1,000’ long weighing 3,000 Ibs. per 
track, at high speed enter all in one direction or in different 
directions, three on the north tracks and three on the south. 
For wind stresses, the structure is supposed to be covered with 
trains of cars, and acted upon with 25 Ibs. per square foot of sur- 
face ; or a wind pressure of 100 dbs. per square foot of bridge for 
a length of 300’ only. The allowed stresses are as follows :— 
Cables in tension, 54,000 ibs: per square inch on the wires in the 
cables ; suspenders, 30,000 Ibs. per square inch in the wires ; cross 
Stays, 60,000 Ibs. per square inch in the wires; anchor bars, 
20,000 Ibs. per square inch. Stiffening trusses—The chords of the 
stiffening trusses when subject to tension only, shall not be strained 
above 18,000 tbs. per square inch of net section for live loads or 
22,500 Ibs. by the combined action of live loads, temperature, and 
wind. Mr. Cooper gives special formule for the allowed stresses 
in other parts similar to those given in his standard specifications 
for steel bridges, also a formule for members subject to reversal 
of stresses by live loads. 
Mr. L. L. Buck has in hand three very large bridges, and has 
completed the designs and commenced to build an arch bridge of 
840’ span, with a central rise of 150’, giving a headway in the 
centre of 170’. This magnificent structure is now in course of 
erection across the Niagra Gorge, for the Niagra Falls and Clifton 
Suspension Bridge Company. The arch ribs are 26’ deep and are 
Spaced 68’ 7” apart at the springing, narrowing to 30° in the centre. 
Mr. L. L. Buck has designed another arch bridge to replace the 
existing railroad suspension bridge at Niagra, and he is chief 
engineer “for building the new East River bridge between New 
York and Brooklyn. 
I met Sir J. Fowler and Sir B. Baker in England, and visited 
the great Forth Bridge. I also had several interviews with Sir 
W. Arrol, the contractor of the Forth, Tay, and Tower bridges. 
In regard to bridge manufacture, the Pencoyd and Athens 
Bridge Works are well equipped with special machinery for 
