ANNUAL ADDRESS. IX. 
was given to the Drake and Stratton Company, and for the super- 
structure to the Union Bridge Company. The two main spans of 
this bridge are 439’ 3” measured between the centres of the end 
Pins, it is of the bowstring type 79’ deep in the centre and spaced 
44’ 6” apart centre to centre. The panel lengths are each 29' 3”. 
The floor is designed to carry a live load of 100 ibs. per square 
foot, or thirty tons on two pairs of wheels 10’ apart. The main 
trusses are proportioned for a moving load of 80 ibs. per square 
foot of floor surface, 40 Ibs. per square foot of side walk, and 130 Ibs. 
per square foot of roadway. The lateral and sway bracing is pro- 
portioned for 250 Ibs. per lineal foot of span. The range of tem- 
perature allowed for is + 75° F., and the maximum stresses in 
the various members are in accordance with the allowed stresses 
given in Mr. Cooper’s specification of highway bridges. The 
masonry of the piers consist of rock-ranged work with rubble 
backing. In this bridge there was no attempt to go down to rock 
either by excavation or driving piles, as it was about sixty feet 
below the bed of the river, but it was necessary to found the piers 
below the reach of scour, on the firm gravel bed which exists for — 
many feet in depth, and which was considered sufficient for sustain- 
ing the weight of the piers without piling. An open cofferdam 
was used built on the timber grillage, which forms the footing 
courses of the pier, and the bottom was simply dredged out. 
In New York I inspected a large number of bridges in course 
of construction and completed, in company with Professor we 
Burr and Mr. Hutton, and inspected many drawings in the New 
York Central and Hudson River Railway Company’s office with 
Mr. W. Katte. I also had a number of interviews with Mr. 
Theodore Cooper, Mr. L. L. Buck, Mr. C. MacDonald and many 
other prominent men in bridge engineering, and I am indebted to 
these gentlemen for the valuable information I received, and for 
their uniform kindness in providing me with drawings and assist- 
ing me in the study of their works. I will direct your attention 
to a few of the more interesting of the bridges :—The Park Avenue 
Improvements, at the time of my visit in course of construction, 
