the Kansas City, Pittsburg, and Gulf Railroad Company to design some bridges. After a little persuasion the General Manager was induced to agree to build a 100-ft. "A" truss span as an experiment; but when he saw the completed plans he ordered at once four bridges to be built therefrom, and this style of structure was soon afterwards adopted as the standard 100-ft. span for the road.

These bridges have shown such rigidity under traffic that they have been used on the St. Louis Southwestern Railway, and have been adopted as the standard for spans between sixty-five feet and one hundred and sixteen feet by the Nippon Railway Company of Japan.

The advantages of this type of bridge are great rigidity in all directions, ease and cheapness of erection, and economy of metal when it is compared with structures of other types having equal strength and rigidity.

IMPACT.

The uncertainty as to the magnitude of the effect of impact on bridges has for many years been a stumbling-block in the path of systemization of bridge-designing, and will continue to be so until some one makes all exhaustive series of experiments upon the actual intensities of working stresses on all main members of modern bridges of the various types. The making of these experiments has long been a dream of the author's, and it now looks as if it would amount to more than a mere dream; for the reason that the general manager of one of the principal Western railroads has agreed to join the author in the making of a number of such experiments on certain bridges of the author's designing, the railroad company to furnish the train and all facilities, and the general manager and the author to provide the apparatus and experimenters. It is only lack of time that has prevented these experiments front being made this year, and it is expected that they will be finished in 1898. It is hoped that the result

of the experiments will be either to determine a proper formula or curve of percentages of impact for railroad bridges, or else to