spans of 775 feet each, when for all reversals an addition of seventy-five (75) per cent of each stress to the other stress was made, and when the effect of reversion was entirely ignored, was only two and a half (2 1/2) per cent. Of this one and a half (l 1/2) per cent were due directly to the increase in the sections of the pieces in which reversion occurred, and one (1) per cent to the augmented dead load. Such being the case, and in view of our limited knowledge concerning the wearing effects of stress reversal, it seems hardly worth while at present to make any change in the practice prescribed in "Bridge Engineering." On the other hand, though, to be perfectly fair, it should be pointed out that reversal of stress may have a greater effect on some other kinds of bridges, such as arches, than it does on continuous- truss structures.

Until the appearance of the January, 1920, issue of the Bulletin of the American Railway Engineering Association, no writer of bridge specifications, as far as the author knows, had ever attempted to specify intensities of working stresses for combinations of live and dead load stresses with secondary stresses. In the Report of "Committee XV—On Iron and Steel Structures" (of which, by the way, the author is a member), published in that issue, there appears the following clause, numbered 47:

Secondary Stresses:

Designing and detailing shall be done so as to avoid secondary stresses as far as possible. In ordinary trusses without subpaneling, no account usually need be taken of the secondary stresses in any member whose width, measured in the plane of the truss, is less than one-tenth of its length. Where this ratio is exceeded, or where subpaneling is used, secondary stresses due to deflection of the truss shall be computed. The unit stresses specified in Article 38 may be increased one-third for a combination of the secondary stresses with the axial stresses.

This allowance of thirty-three and a third per cent applies only to combinations of live load, centrifugal load, impact, and dead load with secondary stresses; but if other loadings, such as wind loads, traction loads, and temperature effects, are added to the combination, the increment of intensity ought to be increased, according to the designer's judgment, up to a limit of fifty per cent.

There is an important question now before the engineering profession for settlement, which, strictly speaking, is one of economics, viz.: the proper relation between intensities of working stresses for bridge members in tension and compression. In the author's opinion, there is no valid reason for the drastic cut in compression intensities made of late in bridge specifications by several of the leading technical societies. Concerning this question he wrote for the Jan. 16, 1919, issue of Engineering News Record the following communication:

The report of the Committee on Column Tests of the American Society of Civil Engineers appears to have caused some fright among bridge designers; for I notice that, the Engineering Institute of Canada has lately published a "General Specification for Steel Railway Bridges" in which the unit stress for columns is given by the formula,