N.Y., which is described in the Engineering Record of Aug. 21, 1897.

Several years ago the author figured on a bridge of this type, but abandoned the design because he deemed it inferior to several others which he prepared for the same crossing.

An excellent type of bascule bridge is that of the Sixteenth Street Bridge over the Menominee Canal at Milwaukee, Wis. It is described in Engineering News of March 7, 1895. The peculiar feature of this design is that, during motion, the centre of gravity of the mass travels in a horizontal plane, thus reducing to zero the lifting effort for the machinery.

A temporary bascule of peculiar detail was used for several years at the crossing of the Harlem River on the New York Central and Hudson River Railroad. It is described in the Railroad Gazette of June 10, 1892. The characteristic feature of this structure, which by the way is a rather clumsy contrivance, is the picking up and dropping of small counterweights while lowering or raising the span.

There is a serious objection to all large bascule bridges, viz., the great surface opposed to the wind by the leaf or leaves when the bridge is being opened or closed. To overcome this pressure powerful machinery has to be used; and it is by no means improbable that even such machinery will be stalled when a high wind prevails.

The jack-knife or folding bridge is a type of structure which is not at all likely to become common. There have been only two or three of them built thus far, and they have been often out of order; moreover, considering the size and weight of bridge, the machinery used is powerful and expensive. The load on the machinery while either opening or closing the bridge is far from uniform, and the structure at times almost seems to groan from the hard labor. The characteristic

feature of the jack-knife bridge is the folding of the two bascule leaves at mid-length of same when the bridge is opened. The loose-jointedness involved by this detail is by no means conducive to rigidity; nevertheless these structures are stiffer than one would suppose from an examination of the drawings.  The Canal Street Bridge,  Chicago,  is of this type; and its