MEANS OF COMMUNICATION. 45 
horizontally by rods of different lengths from these cables, we shall have 
the rough idea of a suspension bridge. 
At first chains were used for this purpose, made something after the 
manner of watch chains with links 10 to 15 feet in length, but it was found 
that cables made of a great number of iron wires bound together were pre- 
ferable on many accounts to chains, which they have almost entirely 
replaced in the construction of suspension bridges. 
By means of bridges upon this principle distances are now spanned, and 
ravines and gorges bridged, which before their introduction were never 
attempted. 
The difficulties of constructing a bridge across the Danube have long been 
considered insurmountable ; the current is very rapid, and the least depth of 
water is 20 feet, while at times the water rises 36 feet above low-water 
mark, bringing with it immense masses of ice which break down embank- 
ments and carry away whatever impedes its progress. Suspension bridges 
have, however, been found to be perfectly practicable; and one constructed 
at Pesth by an English engineer is said to be the first permanent bridge 
erected over the Danube below Vienna for upwards of seventeen centuries. 
It was opened for the first time on the 5th January, 1849, and the same day 
was put to the severest test to which the stability of a bridge can be subjected, 
by the retreat of the Hungarian army over it, followed by the Austrians. 
The passage over the bridge is thus described in a letter written from the 
spot. ‘First came the Hungarians in full retreat, and in the greatest 
disorder, hotly pursued by the victorious Imperialists ; squadrons of cavalry 
and artillery in full gallop, backed by thousands of infantry; in fact the 
whole platform was one mass of moving soldiers; and during the two first 
days 60,000 imperial troops, with 270 pieces of cannon, passed over the 
bridge.” This fact is of the first importance, as it proves that suspension 
bridges, when properly constructed, may be erected on the most exposed 
situations, while their cost is small in comparison with that of stone bridges. 
It should be mentioned in connexion with the above, that the marching of 
a close column of infantry is considered to be the severest test to which a 
bridge can be subjected. The distance between the points of suspension of 
this bridge is 665 feet, and the platform is 42 feet wide. This is the first 
bridge with stone piers built between Ratisbon and the Black Sea since the 
time of Trajan, A. p. 103, when a bridge was built across the Danube near 
the confines of Hungary and Servia, the ruins of which are still pointed out. 
At Vienna a steel suspension bridge has been erected over the Danube, 
the span of which is 234 feet. It is calculated that the weight of the steel 
in the bridge is only one half that of the iron required to build a bridge of 
equal strength. 
The first suspension bridge in England appears to have been erected over 
the Tees, for the use of the miners in 1741. The most noted of this descrip- 
tion in England is the chain bridge over the Menai straits, which separate 
the island of Anglesea from the county of Caernarvon. 
The main opening is 560 feet between the points of suspension; in 
addition there are four arches on the western side and three on the eastern 
ICONOGRAPHIC ENCYCLOPZDIA,—VOL, Ivy. 40 625 
