and reloading take place. Meanwhile Cage 3 arrives and runs into the outer chamber of the traveler, after which the latter is moved to its outer position, so as to allow Cage 3 to unload and reload. This brings Cage 1 into position to begin its return journey; and, after the proper interval, Cage 2 also starts back. Next, when Cage 3 is loaded, the traveler moves inward so as to permit that cage to start. This operation is repeated at the other end of the structure.

The operation of the other track is similar; and, as previously indicated, the times of starting the two groups of cages are adjusted so as to make the intervals between all cages as nearly uniform as practicable.

The time of travel was figured as follows for the round trip of one cage: Assuming that the said cage is in its pocket, loaded and ready to start, then

Trip across structure 3,100 ft. @ 30 miles per hour = 1.17 min.

or, to allow for acceleration and retardation, say   1.50 min.

Wait of two one-minute intervals between cages, which time

will suffice for one lateral transfer and the unloading and the

reloading of the cage  2.00 min.

One side shift of traveler   0.25 min.

Return trip   1.50 min.

Two intervals of one minute each between cages   2.00 min.

One side shift of traveler      0.25 min.

Total time for one round trip   7.50 min.

The number of round trips per hour for each cage will be 60 ÷ 7.5 = 8; and, as there are six cages, there will be altogether 48 round trips made on the two tracks.

The intervals between cages on each track in the same direction will be one min., one min., and five and a half min. By starting the first cage of the group of three on Track "B" one and three-quarters minutes after the third cage on Track "A" has left, the intervals between starts at either end would be as follows:

1 min., 1 min., 1 3/4 min., 1 min., 1 min., 1 3/4 min., 1 min.,

1 min., 1 3/4 min., 1 min., etc., etc.,

Under the assumption of cars one hundred feet long, the capacity of the structure per hour in each direction was estimated to be 48,000 persons plus a large but unknown amount of freight. Assuming also that one-fourth of the people of Algiers would go to New Orleans every day, and that one-half of this number would pass over in a space of three consecutive hours, this structure would comfortably accommodate two cities, each having a population of a million. On the basis, however, of the accommodation of passenger automobiles and motor trucks in the proportion of those operating in  the  City of New Orleans, viz.,  three  automobiles  to each motor-truck with  one  auto—vehicle  to  each  33  inhabitants,  and  assuming