CORNISH VIADUCTS. 



229 



main line of railway. The piers were then ready to receive 

 the iron work. This consisted primarily of two main lattice 

 girders to each span, each weighing fifteen tons, 66 feet long, 

 and 9 feet high, placed 16 feet apart. They were of a some- 

 what box-latticed construction, the top and bottom booms 

 being of this form, 



and the verti- 

 cals thus (like 

 the web of an _i 

 ordinary gir de 



with bar diagonals of various widths. The lower boom was 

 therefore quite hollow, but was provided with a bearing- 

 plate, where it rested on the bed stones. The cross girders, 

 which were ordinary plats girders, were attached to the 

 verticals about half-way up, being strutted also from the 

 main girders by means of T bars. Upon them came the 

 longitudinal rail girders, which, together with the main 

 girders, carried the decking. This consisted of Barlow rails 

 laid side by side. The girders were built by contract, at 

 Cheltenham, and sent down to the Westwood quarry, which 

 • is close at hand, on a special truck. From the siding the 

 main girders were taken out as required, hanging from the 

 ends of two 10-ton travelling cranes drawn along by a loco- 

 motive. They were then swung over the side of the old via- 

 duct and lowered into place. '' Two girders have been thus 

 fetched from the siding one after another, brought out to the 

 viaduct, lowered into place, and the cranes put back in the 

 siding in less than an hour." In a letter the author received 

 the other day from the resident engineer, he mentioned that 

 they were taking a main girder out to Largin Viaduct that 

 very afternoon. The large girders having being placed, the . 

 cross girders were brought out by the main-line travelling 



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