228 COKNISH VIADUCTS. 



train. The traffic was not disturbed for a single day, 

 although the very decking upon which the permanent way 

 was laid was taken up and replaced. 



St. Pinnock Viaduct is 211 yards long, and 151 feet high, 

 and is the loftiest viaduct on the Cornwall Bailway. The 

 masonry piers of the old viaduct, which was built for a 

 single broad gauge, were in such good condition that it was 

 decided to raise them 23 feet, so as to carry, outside the 

 timber works, wrought-iron girders, with a floor of sufficient 

 width to admit of two lines of narrow-gauge rails. It was 

 very fortunate that the old piers admitted of this mode of 

 construction ; for to have entirely rebuilt so lofty a viaduct 

 would have cost quite double as much as what it eventually 

 came to. St Pinnock Viaduct consists of eight central spans 

 of 6G feet (centre to centre of piers), and two short end ones 

 of 50 feet. It was renewed by the Company themselves, and 

 was opened for traffic in 1882. 



The general course of alterations can be described as 

 follows : Temporary ways were first of all constructed on 

 baulks projecting from the viaduct on both sides, in order to 

 balance. Small hand cranes worked upon them, and by 

 these means the piers were built up to the required level. 

 The advantage of these temporary ways was that the main 

 line was thus kept perfectly clear. Whilst raising the piers 

 the timber struts had, of course, to be interfered with as little 

 as possible, or the whole viaduct might have come down. 

 For this purpose a large arched opening was left in the centre 

 of pier and the inner struts were drawn into it. The outer 

 struts which could not be moved were built round and drawn 

 out afterwards. The diagonal bracing was removed to the 

 inner struts. On the new tops of the piers large bed stones for 

 the main girders were set. These stones were each five tons 

 in weight, and were lowered by a travelling crane from the 



