GREAT ACHIEVEMENTS IN BRIDGE BUILDING 71 
the builder as soon as prototypes had been established in 
wood, but it had no place in the construction of bridges of 
any except those of the smaliest size until the Roman era 
began. The employment of the arch for long spans by 
these master builders gave rise to the construction in stone 
of scores of magnificent bridges and aqueducts which excite 
the admiration of engineers the world over to-day. Follow- 
ing the example thus set, many fine stone bridges were 
constructed throughout Europe and particularly in France. 
Until the construction of the Luxemburg stone arch bridge 
with its 278 foot span in 1902, the boldest masonry bridge 
ever built was that constructed in 1380, A.D., over the 
Adda River, at Trezzo, by order of the Duke of Milan. It 
contained an arch span of 251 feet in length, but the struc- 
ture was unfortunately destroyed soon after it was built. 
In 1905 all previous records in masonry bridge construction 
were eclipsed by the great arch span of 295 feet at Plauen 
in Saxony. 
| In the latter part of the eighteenth century the appli- 
cation of cast iron to bridge construction inaugurated a new 
era in that science. At first it was employed only in arches, 
because of its great compressive strength, but later it had 
an extensive use for girders, particularly in Great Britain. 
Gradually it was displaced, however, by the much more 
reliable material, wrought iron, which in turn gave way to 
steel. The early arches of cast metal never actually 
exceeded 240 feet in span, that of the Southwark Bridge, _ 
London, although they were designed up to 450 feet in 
span. 
With the development of the iron and steel industry 
structures of great magnitude and boldness were speedily 
multiplied. The longer spans were at first exclusively of 
the suspension type, until simple trusses and the cantilever 
were developed for structure of large proportions. In 
Great Britain failure to adopt the suspension bridge to rail- 
way traffic led Robert Stephenson, son of the illustrious - 
