secure a large capacity, it would be advisable to make the cages three-decked, and possibly longer than fifty feet. Again, in order to save time in unloading and reloading, the street-cars leaving the city side could take the lower deck and the automobiles and other vehicles leaving the same could occupy the middle deck, the pedestrians, of course, always using the upper deck. Starting from the other side, the automobiles could occupy the lower deck, and the street-cars the middle deck. By this arrangement the climbing of the comparatively steep grade at the North end from the lower-deck level would be done by street-cars only, and time would be saved by holding the automobiles and horse-drawn vehicles in a corral until after the street-car has left clear both the cage and the portion of the approach close thereto. Similarly, the street-car would be held in a corral until after all the other vehicles have gotten out of the way. Barring interference from navigation, each cage could make a round trip in about 32 minutes, which would give 17 round trips per hour, or 34 trips per hour in each direction by the two cages. A 60 ft.-cage would carry two street-cars, eight auto-vehicles, and 300 pedestrians, making 68 cars, 272 auto-vehicles, and 10,200 pedestrians per hour in each direction. Allowing for interruptions from navigation, which would not be serious, because of the great clearance beneath the cages that would permit a large proportion of passing craft to go by without stopping operation, it would be legitimate to count upon a maximum limit of 60 street-cars, 240 automobiles, and 9,000 pedestrians per hour in each direction. Deducting liberally for service to outlying towns, the remaining capacity would be great enough to provide for a population of at least 75,000 persons, or 15,000 per square mile, which is fairly dense for a residence district.

Fig. 32g shows in skeleton outline the elevation of this transbordeur span with a short portion of each of the adjacent approaches, also a cross-section of the structure at mid-span. From this drawing it will be seen that, in reality, there are two distinct, parallel, cantilever bridges located a short distance apart and connected to each other by cross-girders and bracing, leaving ample space between for the safe passage of the two cages; that the latter pass shoreward beyond each main pier a distance equal to one panel-length of the anchor arm, connecting to an approach deck that is suspended from the other two panel points of the said anchor arm; that all the panels of the entire structure are of equal length, there being three of then in each anchor arm, five in each cantilever arm, and six in the suspended span; and that the outlines of all chords are parabolic curves. Each main pier consists of four pneumatic cylinders sunk to bed rock, each cylinder, being surmounted by a truncated concrete cone, and the three spaces between the four cones being filled with thin, reinforced-concrete walls. Each anchor-pier shaft consists of a mass of concrete supported upon a concrete base that rests on piles. The author believes that the bold, curved  outlines  of  the  trusses,  in  spite of the horizontal line of girders between the  twin  spans,  would make  an aesthetic  structure  that  would  be