GREAT ACHIEVEMENTS IN BRIDGE BUILDING 73 
their work in order that a structure of undoubted safety 
would be provided. Of even greater proportions was to 
have been the ill-fated Quebec Bridge. The central span of 
1,800 feet would have surpassed by nine feet the two great 
spans of the Forth Bridge. While its collapse has been a 
personal blow to the engineering profession, it is comfort- 
ing to reflect that just as the extraordinary security of the 
Forth Bridge was an outgrowth of the disastrous failure of 
the Tay Bridge, so the new Quebec Bridge will be of un- 
doubted safety because of the fall of the first one. 
It was but natural that the excellent qualities of 
wrought iron and steel for engineering structures should 
have been employed frequently in that most pleasing type 
of bridge—the arch. Following the precedents set by the 
early constructors in cast irom, great structures of tiis type 
have been thrown across our streams and gorges.. The 
Eads Bridge at St. Louis, and the two arches over the 
Niagara gorge, and the lofty arch over the Zambesi River, 
below the Victoria Falls, South Africa, are excellent 
examples of such work. The Upper Niagara arch, with its 
linmense span of 840 feet, exceeds in size all other arches ever 
built. 
With the phenomenal development in the use of rein- 
forced concrete have come some very bold bridges of this 
material. The Wainut Lane Arch Bridge at Philadelphia 
contains a span of 233 feet clear, the largest ever completed 
of this material. At the present time there is under con- 
struction at Cleveland a bridge over the Rocky River which 
will have a central arch span of 280 feet in length. 
That the bridge engineer has many surprises in store 
for him, there is no doubt. Two colossal structures which 
have been proposed and are being discussed at the present 
time are a suspension bridge over ithe North River at New 
York, containing a 3,000 foot span, and the Hudson 
Memorial reinforced — concrete arch bridge over the 
Spuyten Duyvil Creek, at New York, containing an arch 
span of 703 feet in length. 
