254 



ENGINEERING. 



scaffolding more easily than their brethren who 

 are engaged in a similar task on the Firth of 

 Forth. Mr. William Arrol was the supervising 

 engineer of the whole work, and he has dis- 

 charged his duties so satisfactorily, that his place 

 as a bridge engineer is assured. As regards the 

 possible recurrence of such a disaster as startled 

 the civilized world in 1879, all confidence may 

 be felt. A wind-pressure of 65 pounds per 



bridge can be opened in five minutes. Cap- 

 stans are provided for operating the mechan- 

 ism by hand-power in case of necessity, the 

 time required being seventeen minutes. The 

 structure was opened for public use on May 22, 

 with imposing ceremonies. The distance be- 

 tween the axes of rotation is 220 feet (nearly). 

 The total weight of the iron-work is 526 tons, 

 with a counterbalance of 532 tons. The clear 



LIFTING BBIDGE AT TARANTO, ITALY. 



square foot has been provided for, and every 

 part of the foundation has been tested to one 

 third more than the greatest possible load that 

 can be placed upon it. 



Bridge at Taranto, Italy. A strait separates 

 the old and new towns of Taranto, and con- 

 nects what is known as the Little Sea (Mare 

 Piccolo) with the Gulf of Taranto, both of 

 classic fame and of considerable maritime im- 

 portance. The bridge recently finished was 

 constructed with a view to the ready passage 

 of large vessels. It consists of two half-arcs 

 meeting above the middle of the strait. Each 

 half is moved by machinery driven by two 

 turbines of 14-horse power. The halves are 

 raised and rotated, the lifting motion being 

 given by four nuts worked by an endless screw, 

 and the rotation effected through large wheels 

 at the end of the abutment. The turbines are 

 driven by water from a reservoir, and the 



distance between abutments is 188 feet. A 

 test-load of 280 tons was left for 24 hours upon 

 the bridge, and caused a deflection of less than 

 3 inches, or about half what was allowed in 

 the specifications. On the removal of the load, 

 the deflection disappeared altogether. 



Stiffened Suspension Bridges. A peculiar type 

 of suspension bridge, known as Garson's pat- 

 ent, has been adopted by the British authori- 

 ties in India, which is believed to secure greater 

 stability with less weight of metal, for small 

 bridges, than any previously adopted plan. The 

 usual plan has been to adopt side girders for 

 small suspension bridges, but this involved too 

 much weight and too great cost. The distri- 

 bution of stress is stated as follows : Upper 

 chain. Stress at center equal to zero, increases 

 toward piers until it reaches a maximum. 

 Lower horizontal member. Stress at abutments 

 equal to zero, increases toward center, where it 



STIFFENED SUSPENSION BRIDGE. SIDE VIEW. 



