member shall be permitted, if it can possibly be avoided; otherwise, the greatest care must be taken to provide ample strength and rigidity for every portion of the structure affected by such torsion.

8. In designing all pin-connected work ample clearance for packing must be provided, and ample room must be left for assembling members in confined spaces.

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

10. In trestles and elevated railroads, the columns must be carried up to the tops of the cross-girders or longitudinal girders, and must be effectively riveted thereto. In no case will it be permitted to cut off the columns and rest the cross-girders or longitudinal girders on top of same.

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

12. In trestles and elevated railroads, every column must be anchored so firmly to its pedestal that failure by overturning or rupture could not occur in the neighborhood of the foot if the bent were tested to destruction.

13. The amount of field-riveting must be reduced to a minimum, without, however, diminishing the number of rivets requisite for strength and rigidity. Whenever it is practicable, all designs are to be made so that the field-rivets can be driven readily.

14. Rivets are not to be used in direct tension.

15. For members of any importance, more than two rivets are to be used for each connection.

16. In designing short members of open-webbed, riveted work, it is better to increase the sectional area of the piece from ten (10) to twenty-five (25) per cent beyond the theoretical requirement than to try to develop the strength by using supplementary angles at the ends to connect to the plates.

17. Star struts formed of two angles with occasional short