Systems of Military Bridges in Use by the United States Army, Those Adopted by the Great European Powers, and Such as Are Employed in British India

With Directions for the Preservation, Destruction, and Reestablishment of Bridges. By Brigadier-General GEORGE W. CULLUM, Lieutenant-Colonel, Corps of Engineers, U. S. Army, Chief of Staff of the General-in-Chief, etc., etc. New York : D. Van Nostrand.
A NATION can hardly achieve military success without paying special heed to its materiel of war. It is the explicit duty of a nation’s constituted guardians assiduously to apply all the resources of science and art, of theory and practice, of experience and invention, of judgment and genius, to the systematic production of the best military apparatus. Ordnance and ordnance stores, arms and equipments, commissary and quartermaster supplies, the means of transportation, fortifications and engineer-trains, navies and naval appliances,— these are the material elements of military strength, which decide the fate of nations. If in these we are behind the age, our delinquency must he atoned by disaster and wasted lives. Civilization conquers barbarism chiefly by its superior skill in the construction and use of the material instruments of warfare. Courage and conduct are certainly important factors in all legitimate successes; but they must work through material means, and are emphasized or nullified by the skill or rudeness exhibited in the device and fabrication of those means. The great contest now in progress has taught us afresh the potency of those material agencies through which patriotic zeal must act, and we shall hereafter lack all good excuse for not having the very best attainable system of producing, preserving, providing, and using whatever implements, supplies, and muniments our future may demand.
As an aid in this direction, we welcome the truly valuable book which General Cullum has now supplied on one of the special branches of military materiel. We owe him thanks for his treatise on military bridges, which was nearly as much needed as though we had not already the works of Sir Howard Douglas, Drien, Haillot, and Meurdra, and the chapters on bridges by Laisne and Duane. General Cullum’s work has more precision and is more available for practical guidance than any other. The absolute thoroughness with which the India-rubber pontoon system is described by him gives a basis for appreciating the other systems described in outline.
It is hardly too much to say that we owe to General Cullum more than to any other person the development in our service of systematic instruction in pontoniering. Before the Mexican War, Cullum and Halleck had ably argued the necessity of organizing engineer troops to be specially instructed as sappers, miners, and ponton-iers. In an article on "Army Organization,” in the “ Democratic Review,” were cited a striking series of instances in which bridge-trains or their lack had decided the issue of grand operations. The history of Napoleon’s campaigns abounds in proofs of their necessity, and the testimony of the Great Captain was most emphatic on this point. His Placentia and Beresina crossings are specially instructive. The well - sustained argument of the article on “ Army Organization" was a most effective aid to General Totten’s efforts as Chief Engineer to secure the organization of our first engineer company. This company proved to he the well-timed and successful school in which our pontoon - drill grew up and became available for use in the present war. There are now four regular companies and several volunteer regiments of engineer troops, whose services are too highly valued to be hereafter ignored.
In 1846, General Taylor reported, that, after the victories of Palo Alto and Resaca de la Palma, a pontoon-train would have enabled him to cross the Rio Grande “ on the evening of the battle,” take Matamoras "with all the artillery and stores of the enemy and a great number of prisoners,— in short, to destroy entirely the Mexican army.” This striking evidence of the necessity of bridge - equipages as part of the material of army-trains coincided with the organization of the first engineer company, and led to the preparation of pontoon-trains for General Taylor and General Scott. General (then Captain) Cullum “had the almost exclusive supervision, devising, building, and preparing for service ” of these trains, and of that used for instruction at West Point. To him is chiefly due the formation of the system ot military bridges with India-rubber pontoons, which was most fully described and illustrated in the original memoir from which the volume now just published has grown. He subsequently, as Professor of Practical Engineering at the Military Academy, aided in developing and perfecting the pontoon-drill, — a department in which G. W. Smith, McClellan, and Duane ably and successfully labored.
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 he conducted on theatres intersected by rivers will be the importance of its bridgeservice. 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 - materiel. 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 bridgesystem are lightness, facility of transportation, ease of manoeuvre in bridge-formation, stability, security, and economy. It necessarily makes heavy demands for transportation ; and on this account bridgetrains 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 he taken only when there is a reasonable prospect of their being real facilities, 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 Indiarubber 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 bridgetrain which can he 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.