330 



ENGINEERING. 



sions are not extraordinary, but the difficul- 

 ties were enhanced by the dearth of timber 

 for scaffolding in the vicinity, and the high 

 freights that rendered importation of iron ruin- 

 ously expensive. Moreover, the single parts 

 of the main span must be easy to lift and as 



the girder would become impracticable at a 

 point where the arch could still be made with- 

 out difficulty. In examining the photographs 

 and drawings of this bridge it is impossible to 

 avoid noting the resemblance of the central 

 structure to the skeleton of a gigantic quadru- 



THE BLAATTW KBANTZ BRIDGE. 



few as possible. All the ordinary forms of 

 truss were carefully considered, and the ques- 

 tion finally narrowed itself to a comparison 

 between a central independent girder and the 

 arch device finally adopted. These calcula- 

 tions demonstrated beyond controversy that 



CKOSS SECTION AND ELEVATION, 



the proportionate cost of a girder increased 

 more rapidly than that of the arch, as the span 

 was enlarged. In other words, that the eco- 

 nomical advantage of the arch increased with 

 the span. The tables as published show that 



ped, with his feet spread apart and planted 

 upon pedestals of masonry built for the pur- 

 pose in the sides of the ravine. The calcula- 

 tions for economically distributing the strains 

 are most elaborate and ingenious, but their 

 nature precludes the possibility of condensa- 

 tion. They may be 

 found fully illustrated 

 in the "Engineer," vol. 

 lix. 



Bridge at Verona. In 

 1882 the ancient stone 

 structure that since the 

 fourteenth century had 

 spanned the river Adige 

 at Verona was de- 

 stroyed by a flood, and 

 a new structure be- 

 came necessary. It was 

 essential, in view of lia- 

 bility to sudden floods, 

 that there should be a 

 clear span of 291 feet 

 between abutments, 

 and the ordinary form 

 of arch with the road- 

 way above it was inad- 

 missible, since the wa- 

 ter-way would have 

 been seriously obstruct- 

 ed thereby. The bridge, which was complete" 

 early in the year, consists of two main arche 

 girders with two vertical sides in lattice-work. 

 These spring from below the level of the road- 

 way at the abutments and rise to a considera- 



