Most of the contents of this chapter are taken from a paper, having the same title, presented to the Institution of Civil Engineers of Great Britain,* but it is supplemented by some later investigations concerning a proposed crossing of the Delaware River between Philadelphia, Pa., and Camden, N. J., on the preliminary economic studies for which the author had previously been retained.

The "transbordeur," as it was named in France where it was originated by the noted engineer, Monsieur F. Arnodin, or "transporter bridge," as it is called in England where a number of structures of that type have been built, or the "aerial ferry," as it is termed in the United States, where there is only a single example, is a rather inferior substitute for a low-level bridge. The author prefers to adopt the name "transbordeur" not only because of the prior claim of that appellation but also on account of its being shorter than either of the other cognomens; and he is going to take the liberty of anglicizing it hereinafter by omitting to put it in italics. The only excuse for the existence of this type of structure is that its construction is permissible at certain locations where no low-level bridge would be allowed, and where a high-level structure would be unsatisfactory for the crossing traffic. Such conditions exist where the land adjacent to the waterway is low; and where many high-masted vessels have to pass, or where the channel forms the entrance to a harbor of refuge. Under the latter condition, any low-level bridge might prove to be a serious menace to navigation; for it is conceivable that the movable span might get out of order and become immovable for a while during a high wind when vessels are passing through the channel in order to reach the safe harbor beyond.

In comparison with the low-level bridge, the inferior features of the transbordeur are as follows:

First. Its carrying capacity for automobiles during any given length of time is much smaller.

Second. The time necessary for crossing by it, up to the present at least, is much greater.

Third. The costs of both power and labor for operation are higher.

Fourth. While the actual first cost of structure is about the same, or possibly a little less, in respect to general service rendered it is larger.

* The contents of this paper were used by the Editor of Le Génie Civil as the basis of a long editorial, published in two successive issues.

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