adjustable rods of ample section to provide for any possible unequal vertical wind-pressure when the span is open; and the horizontal struts of box or I sections are to be rigidly attached to the columns by large plates, to which the clevises of the adjustable rods attach by means of pins.

A pair of adjustable diagonal rods or rigid struts must be used in the horizontal plane of each vertical panel of tower-bracing, so as to ensure the permanent rectangularity of the section of the tower.

All splices in top and bottom chords, inclined posts, and tower-posts are to be full splices, so as to develop the full strength of the section, even if the computed stresses do not demand such a strength of detail.

The upper lateral system between the inner and the outer hips is to be made of rigid diagonals, capable of taking both tension and compression, and transverse struts of I section, that take firm hold of the upper and lower flanges of the top chords. From inner hip to inner hip the diagonals are to be of adjustable rods; but, as before stated, the rods are to be omitted from the panels next to the hips, so as to ensure a proper travel of the wind-loads to the pivot-pier.

The transverse sway-bracing between trusses is to be made entirely of rigid members, and is to be carried down as low as clearance requirements will permit. In long spans the lower horizontal struts of the vertical sway-bracing must take hold of the vertical posts at the flanges of same, so as to hold the said posts firmly in position.

DETAILS OF DRUM AND TURNTABLE.

The drum must be strong enough to distribute the total load from the span properly over the rollers. In general, it should be made, within reasonable limits, as deep as possible, for the cost for the extra depth will be more than offset by the saving in height of pivot-pier.

The bending moment on the drum is to be computed by the compromise formula,