approval of that length by the then Chief of Engineers of the United States Army, he was told that, in view of the possibility of the Mississippi being navigated in the future by large flotillas of barges, the suggested opening would be too small. Thereupon he made another layout having the same length of vertical-lift span but a clear width between piers of five hundred feet, supporting the towers on the cantilevered ends of the two flanking-spans. This arrangement would permit of the flotilla steamer passing through the opening beneath the raised lift-span and of the barges slipping under the cantilever arms, in case that the current should swing the flotilla broadside to the structure, the said cantilever arms having sufficient vertical clearance above extreme high water to permit such passage under any river condition. When the author submitted this new layout to the local U. S. Engineer officer in charge at New Orleans, the request was made for an economic investigation of the structure with not only the suggested clear openings of 300 and 500 feet, but also with those of 600 and 700 feet, adopting a lift span of 350 feet for the 600-ft. opening and a 400-ft. one for the 700-ft. opening. The result of the investigation showed that the 500-ft. opening was more economic than the 300-ft. one, that the latter made the total cost of structure about the same as did the 600-ft. opening, but that the 700-ft. opening was so decidedly uneconomic as practically to be prohibitive.

Early in 1920 the author's Indian agents in Calcutta wrote asking him whether he could evolve a design for crossing the Hoogly River at their city by a single span in a manner that would comply satisfactorily with certain unusual and extremely drastic physical conditions. These conditions were met by the utilization of the above-mentioned scheme of a vertical lift and cantilever arms, combined with pier foundations of built-up piles of exceedingly great length sunk by jetting. This type of piling was originated by the author so many years ago that he had actually forgotten about the matter and had to resurrect the drawings from an ancient office-file. The layout suggested is shown in Fig. 30a. As can be seen by inspection, it contains still another economic innovation, viz., the supporting of the counterweights, which balance the weight of the moving span, from the tops of the columns over the main piers, thus relieving both the cantilever arms and the anchor arms from stresses due to the said counter-weights. There were some other economic innovations involved in the study and estimate that are not shown on the layout; but it is not necessary to discuss them here.

An alternative design was submitted at the same time to the agents mentioned by substituting a double-leaf bascule for the vertical-lift span, with the statement, however, that the first-described layout is in every way preferable, excepting only for the fact that the bascule design gives an unlimited vertical clearance. The Brown wire-rope type of bascule was used; and the counterweights were placed over the main piers, as in the vertical-lift design.