162 ANNUAL REPORT 
The I-beams were 10 inch 25 pound beams, spaced 3 feet center 
to center. The arches were 18 inches thick at the crown and 21 inches 
thick 10 feet from the spring line. The spans were 74 feet with a rise of 
94 feet. It required but six months to build the two bridges. 
Goat Island Bridge, Niagara —This bridge was erected in 1901, 
by the United States. The length of the bridge from the main land to 
Green Island, the small island where the main structure ends, is 371 
feet. The bridge is divided into three spans: two are 103% feet and 
one is 110 feet long, supported by piers 13% feét wide. The rise of 
the elliptical arches is 10 feet for the two short spans and 11% feet for 
the longest span. The roadway is 20 feet wide with 9% foot walks on 
each side. This bridge is built after the Thacher design with steel ribs 
Spaced 3 feet apart im the concrete, (“Whe Stecltibs are miullt upon 
34 by 6 inch steel plates, one near the top of the arch and the other near 
Fig. 100.—Concrete Bridge at Summer Home of P. D. Armour, Jr., Oconomowoc, Wis. 
the bottom. They are connected with 5 or 34 inch iron rods about every 
30 inches. The top and bottom plates or bars follow the general out- 
lines of the arch’so that at the haunch of the arch the steel members 
are about 6 feet apart. iligh oval “headed” tivets, spacedi16) or 7 
inches apart, are riveted into the top and bottom plates to give greater 
bond between the steel and concrete. There are 13, of these steel 
