348 THE POPULAR SCIENCE MONTHLY. 



delayed through want of means, and unnecessary obstacles interposed 

 by mistaken public officials. Moreover, measured by its capacity, and 

 the limitations imposed on its construction by its relation to the 

 interests of traffic and navigation, it is the cheapest structure ever 

 erected by the genius of man. This will be made evident by a single 

 comparison with the Britannia Tubular Bridge, erected by Stephenson 

 over the Menai Strait. He adopted the tubular principle because he 

 believed that the suspension principle could not be made practical for 

 railway-traffic, although he had to deal with spans not greater than 

 470 feet. He built a structure that contained 10,540 tons of iron, and 

 cost 601,000, or about $3,000,000. Fortunately, he has left a calcu- 

 lation on record as to the possible extension of the tubular girder, 

 showing that it would reach the limits in which it could bear only its 

 own weight (62,000 tons) at 1,570 feet. Now, for a span of 1,600 feet, 

 the Brooklyn Bridge contains but 6,740 tons of material, and will sus- 

 tain seven times its own weight. Its cost is $9,000,000, whereas a 

 tubular bridge for the same span would contain ten times the weight 

 of the metal, and, though costing twice as much money, would be 

 without the ability to do any useful work. 



Roebling, therefore, solved the problem which had defied Stephen- 

 son, and upon his design has been built a successful structure at half 

 the cost of a tubular bridge that would have fallen when loaded in 

 actual use. It is impossible to furnish any more striking proof of the 

 genius which originated and of the economy which constructed this 

 triumph of American engineering. 



We have thus a monument to the public spirit of the two cities, 

 created by an expenditure as honest and as economical as those which 

 gave us the Erie Canal, the Croton Aqueduct, and the Central Park. 

 If it had been otherwise, it would have been a monument to the eternal 

 infamy of the trustees and of the engineers under whose supervision 

 it has been erected ; and this brings me to the final consideration 

 which I feel constrained to offer on this point. 



During all these years of trial and false report a great soul lay in 

 the shadow of death, praying only to stay long enough for the com- 

 pletion of the work to which he had devoted his life. I say a great 

 soul, for in the spring-time of youth, with friends and fortune at his 

 command, he gave himself to his country, and for her sake braved 

 death on many a well-fought battle-field. 'When restored to civil 

 life, his health was sacrificed to the duties which had devolved upon 

 him as the inheritor of his father's fame and the executor of his father's 

 plans. Living only for honor, and freed from the temptations of nar- 

 row means, how is it conceivable that such a man whose approval 

 was necessary to every expenditure should, by conniving with job- 

 bers, throw away more than the life which was dear to him that he 

 might fulfill his destiny and leave to his children the heritage of a 

 good name and the glory of a grand achievement ? Well might this 



