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22 MARINE REVIEW. town. The only existing artificial obstruction below the Aqueduct bridge is the old historic "Long" bridge, which is soon to be replaced by a new bridge to carry the two tracks of the Pennsylvania railroad and another adjacent bridge for highway and electric car traffic, which will form the connecting link between Washington and Mount Vernon. A third bridge has been proposed across the Potomac river, about a [December 12, home to congress the serious question of artificial obstructions in navi- gable channels. If only a bascule bridge was approved by the war depart- ment for the Memorial bridge to Arlington, then it would seem that there is much greater reason for adopting the bascule type of structure in the two bridges about to be built, so close together farther down stream. Fig. 2 on the following page illustrates the difficulty of navigating a merchant or naval vessel through the narrow channels provided by Fig. 4.--Showing the Chicago river artificially obstructed by two center-pier swing bridges, opened in center of channel. mile farther up stream than the two bridges above mentioned, called the " \temorial" bridge, from Washington to Arlington cemetery. For this bridge plans were received and approved by the war department about a year ago. These plans called-for only a bascule or vertically-moving bridge without center pier obstruction, to span the navigable or dredged channel of the Potomac river. The funds for the construction of this bridge were not appropriated by two adjacent swing bridges, and Fig. 3, just under it, shows the clear unobstructed channel and the ease of navigating either the largest merchant or naval vessels through two adjacent bascule bridges. These illustrations are so graphic that further comment is unnecessary. In New York, Boston, Phila- delphia, Bridgeport (Conn.), Chi- cago, Milwaukee, Cleveland, Buf- falo, and many other cities of the United States and foreign coun- tries, center-pier swing bridges are being removed because they form obstructions to navigation and are being replaced by vetti- cally-moving or bascule bridges, in order. to prevent just such channel obstructions as are here spoken of. At the capital of the United States and upon a river of such great importance as the Po- tomac, at the beginning of a new century, it would certainly seem like a serious breach of trust to permit a railroad company to place artificial obstructions in the form of center-piers and large bridge protections, which would stand as a bar impairing naviga- tion for fifty years or more to come. This should not be per- mitted. It is not difficult to under- stand the injustice of permitting the placing of a permanent artifi- cial obstruction in the middle of Broadway, New York city, the middle of State street, Chicago, : or the middle of Pennsylvania avenue at Washington. Yet each of these great public highways has avail- able many adjacent parallel streets. The dredged navigable channel of the Potomac river is the only available artery and should forever be a great public highway serving navigation, more valuable both in times of peace and war than any of the streets mentioned. It is the only available water route and cannot be paralleled by other waterways giving equal facilities the last congress. The last con- fF gress did, however, appropriate | $568,000 for the construction of 'the highway bridge above men- tioned, which forms the connect- ing link between Washington and Mount Vernon. The railroad bridge to be built adjacent to this highway bridge is to be built and paid for by the Baltimore & Poto- mac or Pennsylvania company. Plans of both of these bridges, under the act of congress ap- proved Feb. 12, 1901, must be approved by the secretary of war. The site of the proposed bridges and the curved nature of the channel of the Potomac river at the site of these bridges is shown by the map, Fig. 1. The map also shows the narrow dredged chan- nel marked by buoys. A fepre- sentative of the railroad company submitted for approval a plan consisting of plain Pratt truss fixed spans with a center-pier swing bridge in the middle of the dredged channel to span the navi- gable channel. It is to be hoped in this case as in all similar cases throughout the country that per- mission will not be granted to this railroad company to obstruct the middle of the dredged channel of the Potomac river. If the rail- road bridge is a swing bridge, the adjacent highway bridge to Mount Vernon must of necessity also be a center-pier bridge. The two swing bridges will occupy the middle and best part of the channel, and will be very obstruc- tive to navigation. In fact, in a tidal river, like the Potomac river, such an obstruction is much more serious than a similar obstruction upon the non-tidal rivers around the Great Lakes, where such obstructions have been universally condemned and are rapidly being removed and replaced by bascule or vertically-moving bridges. This Washington matter brings Fig. 5.--Showing the same channel in Chicago river cleared by the removal of the two center-pier a i - ng brid and the substitution of two bascule bridges. . a she for navigation to and from the capital. There is also produced herewith two photographic views--Fig. 4, showing the Chicago river obstructed by two center-pier swing bridges and Fig. 5, showing the clear channel provided by the removal of the two swing bridges and the substitution of two bascule bridges. These illustra-