Kitabı oku: «The Atlantic Monthly, Volume 12, No. 74, December, 1863», sayfa 17

We suppose that all profound and sincere students of military operations are agreed in accepting bridge-trains and skilled pontoniers as among the necessities of grand armies. In proportion as the campaigns which an army is to make are to be conducted on theatres intersected by rivers will be the importance of its bridge-service. Our own country, abounding in rivers of the grandest proportions, will need to be always ready for applying the highest skill and the best bridge-equipage in facilitating such movements as may prove necessary. We accept this as an indispensable part of our organized system of war-matériel. Were other evidences lacking, the experiences of the Chickahominy, Rappahannock, Potomac, and Tennessee will perpetually enforce the argument. The generation which has fought the Battle of Fredericksburg, and which has witnessed Lee's narrow escape near Williamsport, is sufficiently instructed not to question the saving virtues and mobilizing influences of bridge-trains.

The chief essentials in a military bridge-system are lightness, facility of transportation, ease of manœuvre in bridge-formation, stability, security, and economy. It necessarily makes heavy demands for transportation; and on this account bridge-trains have frequently been left behind, when their retention would have proved of the utmost importance. Their true use is to facilitate campaign-movements; and while they should be taken only when there is a reasonable prospect of their being real facilites, they should not be left behind when any such prospect exists. It was in response to the demand for easy transportation that the system for India-rubber pontoons was elaborated. Single supporting cylinders of rubber-coated canvas were first experimentally used in 1836 by Captain John F. Lane, United States army, on the Tallapoosa and Chattahoochee Rivers in Alabama. The service-pontoon, as arranged by General Cullum, is composed of three connected cylinders of rubber-coated canvas, each having three compartments. On these pontoons, when inflated, the bridge-table is built, lashed, and anchored. This bridge has remarkable portability, but it has also serious defects. The oxidation of the sulphur in vulcanized rubber produces sulphuric acid in sufficient amount to impair the strength of the canvas-fibres, thus causing eventual decay, rendering it prudent to renew the pontoons after a year's campaigning. The pontoons are required to be air-tight, and are temporarily made partially useless by punctures, bullet-holes, rents and chafings, although they are easily repaired. Hence this bridge, despite its portability, is hardly equal to all the requirements of service, though it was the main dependence in Banks's operations in Louisiana, and was successfully used in Grant's Mississippi campaign.

General Cullum briefly describes the various bridge-systems employed in the different services of the world, including the galvanized iron boat system, the Blanchard metal cylinder system, the Russian and Fowke's systems of canvas stretched over frames, the Birigo system, the French bateau system, the various trestle systems, and many others. The French wooden bateau is the pontoon chiefly used in our service, and it is specially commended by its thoroughly proved efficiency, and by its utility as an independent boat. Its great weight and the consequent difficulty of its transportation are the great drawbacks, and to this cause may well be ascribed much of the fatal delay before the Fredericksburg crossing.

It is a hopeless problem to devise any bridge-equipage which shall overcome all serious objections. All that should be expected is to reduce the faults to a practical minimum, while meeting the general wants of the service in a satisfactory manner. The lack of mobility in any bridge-train which can be pronounced always trustworthy may, perhaps, compel the adoption, in addition to the bateau-train, of a light equipage for use in quick movements. This will, however, create complication, which is nearly as objectionable here as in the calibre of guns. Thus it is that any solution may prove not exactly the best one for the particular cases which may arise under it. All that should be demanded is, that, by the application of sound judgment to the data which experience and invention afford, our probable wants may be as well met as practicable. Some system we must have; and, on the one hand, zeal for mobility, commendable as it is, must not be permitted to invite grand disasters through failures of the pontoons to do their allotted work; while, on the other hand, a morbid desire to insure absolutely trustworthy solidity of construction must be restrained from imposing needless burdens, which may habitually make our crossings Fredericksburg affairs. Between these extremes lies the right road. American skill has hardly exhausted its resources on this problem. The suspension-bridge train, a description of which General Meigs has published, is deserving of consideration for many cases in campaigns. General Haupt's remarkable railroad-bridges thrown over the Rappahannock River and Potomac Creek, the latter in nine working-days, were structures of such striking and judicious boldness as to justify most hopeful anticipations from the designer's expected treatise on bridge-building. Our national eminence in the art of building wooden trussed and suspension bridges is proof enough that whatever can be done to improve on the military bridge-trains of Europe may be expected at our hands. We shall not lack inventiveness; let us be as careful not to lack judgment, and by all means to be fair and honest in seeking for the best system. When the experience of this war can be generalized, a more positive pontoon-system will be exacted for our service. It is fortunate that this matter is in good hands. While hoping that the close of the present war may, for a long time, end the reign of Mars, it behooves us never again to be caught napping when the Republic is assailed.

RECENT AMERICAN PUBLICATIONS

RECEIVED BY THE EDITORS OF THE ATLANTIC MONTHLY.

The Natural Laws of Husbandry. By Justus von Liebig. Edited by John Blyth, M.D., Professor of Chemistry in Queen's College, Cork. New York. D. Appleton & Co. 12mo. pp. 388. $1.50.

The Constitutional History of England since the Accession of George Third, 1760-1860. By Thomas Erskine May, C.B. In Two Volumes. Vol. II. Boston. Crosby & Nichols. 12mo. pp. 596. $1.50.

The Holy Word in its own Defence: addressed to Bishop Colenso and all other Earnest Seekers after Truth. By Rev. Abiel Silver, Author of "Lectures on the Symbolic Character of the Sacred Scriptures." New York. D. Appleton & Co. 12mo. pp. 305. $1.25.

"Who Breaks Pays." By the Author of "Cousin Stella," etc. Philadelphia. F. Leypoldt. 16mo. paper, pp. 302. 50 cts.