RAILROAD CONSTRUCTION 315 
The bents are connected by stringeivs, each 8 by 14 inches or 
9 by 16 inches in size, which are placed at right angles on top of 
the caps and support the crossties. Two stringers are used under 
each rail. They are spaced 2 inches apart with washers, and 
then bolted together. They may also be drift bolted to the caps 
to hold them in position. Sawed ties,^ 6 by 8 inches by 8 feet, 
are placed 24 inches, center to center, on top of the stringers, 
and are often sunk about ^ inch into them. Every fourth or fifth 
crosstie also is drift-bolted to the stringers. Three- by 8-Lnch 
guard rails are then placed on top of the ends of the ties parallel 
to the stringers and spiked to every other tie to prevent the ties 
from bunching. 
When the trestle is less than 9 feet high it is seldom braced, 
but where the height exceeds this it is braced on each side with 
3- by 6-inch scantlings placed diagonally across each row of piles, 
the top end of the brace being fastened to the cap and the lower 
end to the opposite side of the bent just above the ground. The 
scantlings are spiked to the cap and to each pile. 
Where the bent exceeds 20 feet in height it is divided into two 
or more stories by horizontal braces, of 3- by 8-inch scantlings, 
and each story is braced diagonally in the manner described above. 
At each story every bent is connected by a longitudinal brace. 
Bents over 20 feet in height have five piles whose diameter 
should not be less than one-twentieth of their length. One pile 
is placed in the center of each bent and two others are placed on 
either side at a distance of approximately 24 inches, center to 
center. The two other piles are placed about 1 foot out at 
the top of the bent and are given a batter of 2 inches for each 
foot of height. 
In swampy sections the main line is sometimes built on piling. 
The advantage of this form of road is that a firm foundation is 
secured in places where dirt ballast could not be used, stumps 
need not be removed, and the cost of maintenance for the first 
few years is low. 
In cypress swamps these roads are made of piles from 12 to 
15 inches in diameter, driven down to a solid foundation, which 
may be from 60 to 80 feet. Piles 30 feet long are made from one 
cypress stick but lengths greater than this are secured by placing 
1 Hewed crossties are seldom used for trestle work because of the variation 
in thickness. 
