as to permit of uninterrupted expansion and contraction or to anchor them down fixedly is a mooted question among engineers. The author prefers the former method for the reason that, if all the feet are anchored so as to prevent all motion, either the pedestals will be sprung laterally or the horizontal struts will bulge or be overstrained when the temperature is at its upper extreme range. In determining the method of sliding, one foot of the four should be made fixed in both directions, two should be fixed in one direction only, and the fourth should be free to slide in both rectangular directions.

Occasionally it is advisable to use hinged ends for a solitary bent; but the author generally prefers to fix the feet and let the column spring laterally under changes of temperature, taking care that it be proportioned properly to resist the stresses due to such springing when the same are combined with the other stresses to which the column is subjected. Fixed ends for columns of solitary bents are much more conducive to rigidity of structure than are hinged ends.

The question of sliding ends for longitudinal girders will be treated in the next chapter, which will deal with elevated railroads, the expansion pockets being the same for such structures as for railroad trestles.

The best sections for columns are either two channels laced or four Z bars with a web plate or lacing. If the columns have to carry transverse loads, they should have solid webs instead of lacing, so as to transmit the shear effectively from top to bottom. For light work, four angles in the form of an I with a single line of lacing will suffice.

All columns when spliced should have their splices located about two feet above the panel points of the column bracing. Failure to so locate them will add materially to the cost of erection. All such splices should be made full, more especially when the tension on the column runs high.

In proportioning anchorages, the pedestal weight should be made not less than twice the greatest net uplift from the column, due account being taken of the buoyant effort of the water in case of a possible submergence of pedestal.