be a believer in the doctrines of Wohler and Weyrauch, and in the theory of the fatigue of metals, because one's common sense will lead him to proportion sections of bridge members in accordance with the foregoing views.
      In the specifications given in Chapters XIV. and XVI., the impact formulae and the increased intensities for combinations of stresses involving those due to wind loads take care of this feature of design for all structures excepting high railroad trestles, in which latter the designer's professional judgment cannot well be eliminated.

Principle XXIV.

In all main members having an excess of section above that called for by the greatest combination of stresses, the entire detailing should be proportioned to correspond with the utmost working capacity of the member, and not merely for the greatest total stress to which it may be subjected. In this connection, though, the reduced capacity of single angles connected by one leg only must not be forgotten.

It is almost needless to state that most engineers, especially those connected with contracting companies, will disagree with the author on the correctness of this statement; nevertheless be has yet to see the first case where adherence to the principle would involve improper, clumsy, or inappropriate construction. If it be right, for any reason, to use an extra amount of metal in the section of a member, why is it not also right to design that member throughout so that, if tested to destruction, it would fail as a whole and not in a detail? It seems to the author that the considerations which require extra section would demand either extra strength or extra rigidity, or both, in the details as well as in the section itself.

Principle XXV.

In every bridge and trestle adequate provision must be made for the contraction and expansion of the metal.

Neglecting to comply with this principle has often been the cause of failure and disaster.