A474, REPORT—1899. 
in length for the side spans, and one of 53 metres (174 feet) for the centre. 
It had a single span of 120 metres (410 feet) only while being moved. 
The structure of the temporary bridge was erected on the right bank 
of the river and launched so that the channel left for boats was never 
encumbered and navigation not once interrupted. As the total length 
the contractors had at their disposal for the launching platform was only 
about 60 metres, it was necessary to proceed in three steps. The first 
portions having been delivered in the middle of July, the first launching 
was made on August 20, the second on September 8, the last one on the 
30th of the same month. 
The centreings of the bridge were completed and ready to be used at 
the beginning of November. 
The steel voussoirs were cast at five different steel works, each of 
which received orders for a certain number of arches to be delivered in 
succession :— 
Chatillon & Commentry steel works ‘ 2 . Four arches. 
St. Chamond steel works . ; : : : ; a ag 
Creusot steel works . A j : ; ; . Three ,, 
St. Etienne steel works . : : : 5 . Two Pe 
Firminy steel works : ‘ - : : ey 
Before being delivered each arch was mounted in the manufacturer’s shop 
in halves. On a plain solid platform made of concrete or of timber the 
exact shape of a half-arch was drawn with the utmost precaution ; one of 
the most experienced inspectors went through the five shops to examine 
these drawings, to compare them with the contemplated dimensions, and 
to note the conditions of their structure. 
When it was found that the drawings were satisfactory in every 
respect, and identical with each other, the different voussoirs of each half- 
arch were placed upon them and connected. 
In this way, when leave was given to deliver the voussoirs, the engi- 
neers were assured that no difficulty would arise in the course of the 
operations of erection. They were right in so thinking, because it only 
once happened that an operation was interrupted on account of a joint 
table not being truly planed. 
The first operation made in sitw was the exact measurement of the 
distance between the abutments, which was effected very easily by means 
of the rolling bridge itself considered asa gauge. The measurements 
made in this way in sitw for every arch allowed every thrust stone to be 
properly cut beforehand with satisfactory exactness. 
The travelling bridge had been fitted with four trucks running on 
two elevated systems of rails above the place where the arches were to 
be erected. Hach truck was pulled by a chain from the extremity of 
the bridge above the abutment to its central part, and could stop at any 
intermediate point. The load hung from the truck by means of pulleys 
and cable, so that it could be kept up or down at any height. Cables and 
chains were moved by means of steam winches at each extremity of the 
travelling bridge according to the orders communicated. 
In this way, when the orders were carefully given by the foreman to 
the engine-drivers, the workmen had scarcely any trouble ; the handling 
required only a certain cleverness in the operation of keeping together 
the corresponding bolt-holes by means of crowbars, while each voussoir 
was slowly slipping along the next one that had just been erected. 
