Such a transference would be doubly injurious; because it would throw on some of the girders more live load than they were proportioned to carry, and at the same time it would probably overstrain the diagonals and their connections, and would certainly tend to distort laterally the flange angles of the longitudinal girders.

Principle XXXIII.

In bridges, trestles, and elevated railroads, the thrust from braked trains and the traction should be carried from the stringers or longitudinal girders to the posts or columns without producing any horizontal bending moment on the cross-girders.

This is a late requirement of the author's, that has been employed in his designs for a few years past. Its correctness was established in his before-mentioned paper on Elevated Railroads.

Principle XXXIV.

In trestles and elevated railroads the columns should be carried up to the tops of the cross-girders or longitudinal girders and be effectively riveted thereto.

The correctness of this proposition also was established in the said paper on Elevated Railroads.

Principle XXXV.

Every column that acts as a beam also should have solid webs at right angles to each other, as no reliance can be placed on lacing to carry a transverse load down the column.

The truth of this proposition is evident when one reflects that a single loose rivet or a single bent lacing-bar in the whole line of lacing will prevent the latter from carrying as a web a transverse load. Loose rivets and bent lacing-bars are, unfortunately, not uncommon in structural metal-work.