150 TRANSACTIONS OF THE [MAY 23, 



tory, may not be given up and forgotten, but that it may be re- 

 introduced, whenever circumstances may allow, in order that it 

 may again add beauty to our landscapes, even in rural districts 

 and outside of the limits of ornamented parks and pleasure- 

 grounds, to which it has in modern times been mostly con- 

 fined. 



It should not, however, I think, be considered impossible to 

 add to the skeleton structures in wrought iron, which are now 

 met with at every turn, and which are constantly being multi- 

 plied, simple architectural adjuncts to relieve their uncouth ap- 

 pearances. In one instance, at least, this has been done in this 

 country with marked effect, though the conditions under which 

 the structure was built were certainly unusually favorable in this 

 respect. I allude to the Girard Avenue bridge in Philadelphia, 

 designed and built by the Phoenix Bridge Company, a wrought- 

 iron bridge, which has called forth from many a traveller from 

 foreign lands expressions of delight on account of the architec- 

 tural elegance of its design. 



The history of the development of the art of bridge construc- 

 tion is marked, to a certain extent, by periods or eras coincident 

 either with the introduction of new materials in the arts, or with 

 the necessities which have arisen for compassing greater spans 

 under conditions of heavier traflBc. The suspension bridge, of 

 very ancient origin, has held its place, though to a limited ex- 

 tent, until our own time, when its place is likely to be usurped, 

 to a great degree, by the cantilever. Built in primitive times, 

 with cables of organic material, the introduction of wrought 

 iron and of iron wire furnished facilities of construction and 

 elements of durability and strength which the older suspension 

 bridges did not possess, and the great bridge between this city 

 and Brooklyn may be regarded as the culmination of this sys- 

 tem, and perhaps the most remarkable example which the world 

 is destined to see; there being inherent defects of the system, 

 which render it inapplicable to rapidly moving heavy loads, 

 which will always be a sort of bar to its general use. 



The reverse of the suspension bridge, the arch, of all systems 

 has held the most universal sway, until the long spans met with 

 in the routes of railway communication, and the difficulties of 



