was placed at the middle of the double-track space, and pedestrians had to use the roadway. Of course, there could not be railway and highway vehicles simultaneously on the structure, but the roadway was wide enough for teams to pass and for a line of pedestrians on each side of a railroad train. The end piers of the swing span and all the other piers were built of piles and other timbers, the flanking spans were of the combination type, viz., tension members of steel and compression members of timber, and the approaches were single-track timber-trestles for the railway and wooden approaches with fairly-steep grades for the highway. This temporary work was constructed so as to last at least eight years, and it was used for ten, when it was taken out by the author and replaced with permanent construction for the Illinois Central Railroad Company, which had bought the structure for its main-line entrance into the city of Omaha. The temporary work here described was all so well and thoroughly done that, when it was removed, there were no evidences whatsoever of decay or failure. The author is of the opinion that it could have been used for six or eight years longer without the slightest danger of any kind. The evolution of a design such as above described involves economics of the highest type; and the author considers it to be by no means one of his minor achievements in bridge designing and construction.

There is a matter of economic importance which no promoter should ever forget; and that is the growing scarcity of timber, and, consequently, its greater future price. While it may prove temporarily advantageous to use it in his bridge, he should make sure that the metalwork of his superstructure is strong enough and that the foundations of his substructure are sufficiently substantial to carry properly the increased dead load of the spans due to the future substitution of heavy concrete for light timber.