VIII. as PERCY ALLAN. 
beams, and permitting of easy removal in connection with the 
system to be adopted in renewing chords. 
One of the features of the new type of truss is, that any member 
can be renewed without staging from below, a matter of import- 
ance when deep gorges or fast running streams have to be crossed. 
Briefly stated, the top and bottom chords being in two pieces, the 
Suspension rods are removed and re-arranged so as to throw the 
whole weight on one flitch ; there being no strain on the remaining 
flitch, any member of the top and bottom chord can be replaced 
with sound timber ; and by slacking the suspension rods and 
inserting temporary struts, any of the braces can be renewed, 
whilst the renewal of the cross girders is obviously a simple matter. 
In the superstructure of one of the new 90 feet spans carrying 
a 15 feet deck, there is 500 cubic feet less timber than in the 
1886 type of truss, which, in conjunction with the greater ease 
in framing together (notably in the bottom chord, where no 
fitting is required) the fewer bolt holes to be bored and the short 
lengths of timber employed, effects a saving of over £100 in each 
90 feet span. 
The economy is more marked when it is considered that the 
old trusses were designed to carry a 15 feet carriageway, whereas 
the new trusses are designed to carry two 5 feet footways in 
addition to a 15 feet carriageway. Thus it will be seen that the 
later design of truss bridge offers greater facilities for traffic at a 
much reduced cost. 
The piers carrying truss bridges vary in accord with local Mea 
cumstances ; one of the heavy type is that shown in Plate 6, 
Consisting of nine vertical piles 12” by 12” arranged in groups of 
four under heels of trusses, also one short vertical pile upstream 
and two short vertical piles downstream, carrying up and down- 
stream struts. The pier is stayed with wales and braces 12” by 
6” and internal compression struts 12” by 12” seated on hardwood 
chocks secured to piles with bolts, the chocks being set end on t0 
do away with shrinkage, the previous system of seating butting 
