that for twelve hours per day the cages would run full and the other twelve hours only half full, the proposed transbordeur would serve a population of about 475,000 in Algiers, or, say, 400,000 to allow for interruptions from river traffic. Were the short cages used instead of the long ones, the population that could be served would be 200,000, showing that, for many years to come, even with the short cages, the structure would have ample transporting capacity, because Algiers at present is only a small community.

The next improved layout is shown in Fig. 32c, which indicates that the number of transverse travelers had been increased to six and that the travel on each track is in one direction only. In this case the travelers run on tracks beneath them; but after the drawing had been made, some figuring showed that it would be more economical to suspend the said travelers from tracks overhead, as indicated in the layout of Fig. 32d. In both of these layouts, by using only four cages, one traveler at each end, and 1 3/4 minutes for crossing the river, a service of 2 3/4-minute intervals could be obtained, provided there were no interference from river traffic. With three travelers at each end and five cages, the interval would be reduced to 2 1/4 minutes; and by adding another cage it could be made as small as 1 3/4 minutes. As indicated previously, the final layout with only two travelers at each end gave 2 1/2-minute intervals with four cages and 1 1/2 minute intervals with six cages, thus reducing both the total first cost and the expense of operation.

It is difficult to compare the operating capacity of a transbordeur with that of a low-level bridge of the same general cross-section, but it might be well to make the attempt, assuming as an equivalent low-level structure the layout adopted for New Orleans, viz., the author's standard city-bridge, having a clear roadway of 42 feet with two street-railway tracks at the middle and two exterior sidewalks, each of eight feet clear width.

Assuming three lines of pedestrians per sidewalk with intervals of three feet in each line, which represents as dense a crowd as could cross comfortably, and a speed of three miles per hour, makes 15,840 foot-passengers per hour in each direction, while the transbordeur with 50 ft.-cages could carry about two-thirds of that number. In respect to a combination of street cars and automobiles, the average speed when the roadway is at all crowded will not exceed twelve miles per hour, and in such a case the distance between autos would be about sixty feet. It would be seldom that there would average more than one street car per minute on each track, and in that case there would not be more than one automobile in 120 ft. traveling along the street-car space; hence there would be 1080 + 540 = 1620 automobiles passing in each direction per hour or ten times as many as the 50 ft.-cages would carry. There would be about one and a half times as many street-cars traversing the bridge as could be carried by the transbordeur with the short cages. Were there a horse-drawn vehicle or two on one side of the roadway, especially a heavily loaded one, the average speed for the automobiles would quickly reduce to six miles per hour or less, because the existence of occasional street-cars, as well as the automobiles