566 ANNUAL REPORT SMITHSONIAN INSTITUTION, 1937 



hour, and it is expected that this will be fully utilized by holiday and 

 week-end traffic from the very beginning. 



Having passed through the Gate, our traveler will now without 

 doubt fix his attention on the magnificent structure under which he 

 has just passed. He may have traveled the world over but nowhere 

 has he seen a bridge of such magnitude or graceful beauty. At mid- 

 span it is 230 feet above the water, high enough to let any ship afloat 

 pass underneath with plenty of clearance. It is a mile across, and 

 there is only one pier in the water. That pier is only 1,100 feet from 

 shore; it is 4,200 feet between the towers which support the cables 

 and which in turn support the floor of the bridge. In all his travels 

 he has not seen towers like these. The design gives confidence of 

 strength and stability and at the same time gives that feeling of satis- 

 faction most often inspired by structures that are arcliitecturally 

 correct. An officer of the sliip, standing beside liim, tells liim that the 

 tower tops are 750 feet above the water. The two cables which pass 

 over the tops of the towers and end in massive blocks of concrete back 

 on shore, are 3G}^ inches in diameter — the largest bridge cables ever 

 made. Each cable is 7,650 feet long and contains 27,572 parallel wires 

 about the size of a lead pencil. Eighty thousand miles of wire were 

 required for the two cables — enough to encircle the globe more than 

 three times at the Equator. Eacli cable has an ultimate tensile 

 strength of 200 miUion pounds. Yes, it takes a pretty good anchorage 

 at each end of the cable to withstand this pull. Fortunatelj'', solid 

 rock was found at each end, and big pockets were excavated in this 

 rock to form a setting for the concrete anchorage blocks, each of w^hich 

 contains 30,000 cubic yards. You're right, there is a trick about 

 fastening the cable to the anchorage. You see, the wires of the cable 

 are grouped into 61 strands. Some distance in front of the anchorage 

 a cast steel band is placed around the cable and between that point 

 (called the "splay point") and the anchorage the strands "fan out," 

 so that at the anchorage they are separated by 2)^ feet or more. Each 

 strand is there ancliored to a pair of steel bars w^hich extend back into 

 the concrete for about 130 feet where they terminate in heavy steel 

 girders. 



Our friend realizes at a glance that the entire floor structure of the 

 bridge is suspended from these huge cables. He can see at 50-foot 

 intervals the steel ropes which hang down from the cables and attach 

 to the stiffening trusses. At each point of attachment there are 

 four parts of rope 2*K6 inches in diameter. The concrete roadway 

 and sidewalks are carried directly on tliis suspended steel framework. 

 There it hangs like a great hammock between the giant towers. How 

 far will it sw4ng sideways? That is a fair question. 



The informative officer in liis frequent passing through the Gate has 



