The longitudinal bracing should consist of diagonals of timber of suitable dimensions, in alternate panels, with horizontal struts made continuous at bracing panel points throughout all panels.

In addition to the transverse and longitudinal bracing previously described, all trestles on sharp curves should be provided with a lateral system composed of timber diagonals spiked to caps and to bottoms of stringers.

What has been said in regard to flooring for pile-trestles applies also to framed trestles.

The compression-members, when impact is included in the stresses, are to be proportioned by the formulae

for long-leaf yellow-pine and hard woods, and

for white pine, short-leaf yellow pine, and soft woods, in which formulae l and b are respectively, in the same unit, the unsupported length and the least transverse dimension of the strut.

SPECIFICATIONS FOR TIMBER TRESTLES.

CLEARING AWAY RUBBISH AND PREPARING GROUND FOR
STARTING WORK.

Before beginning work on any trestle, all rubbish, logs, trees, and brush must be cleared away, and all combustible material must be burned or removed for the entire width of the right-of-way.

DIMENSIONS

All posts, braces, stringers, ties, guard-rails, sills, and all timber generally, shall be of the exact dimensions given and figured in the drawings.  No variations from these will be