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OF THE CONSTRUCTION OF IRON BRIDGES.
As bridges, and the method of constructing them, are becoming objects of great importance throughout the United States, and as there are at this time proposals for a bridge over the Delaware, and also a bridge beginning to be erected over the Schuylkill at Philadelphia, 1 present the public with some account of the construction of iron bridges.
The following memoir on that subject, written last winter at the Federal City, was intended to be presented to Congress. But as the session would necessarily be short, and as several of its members would be replaced by new elections on the ensuing session, it was judged better to let it lie over. In the mean time, on account of the bridges now in contemplation, or began, I give the memoir the opportunity of appearing before the public and the persons concerned in those works.
Bordentown on the Delaware,
To the Congress of the United States.
I Have deposited in the office of the Secretary of State, and under the care of the patent office, two models of iron bridges; the one in pasteboard, the other cast in metal. As they will shew by inspection the manner of constructing iron bridges, I shall not take up the time of Congress with a description by words.
My intention in presenting this memoir to Congress is to put the country in possession of the means and of the right of making use of the construction freely ; as I do not intend to take any patent right for it.
As America abounds in rivers that interrupt the land communication, and as by the violence of floods, and the breaking up of the ice in the spring, the bridges, depending for support from the bottom of the river, are frequently carried away, I turned my attention, after the revolutionary war was over, to find a method of constructing an arch, that might, without rendering the height inconvenient, or the ascent difficult, extend at once from shore to shore, over rivers of three, four, or five hundred feet, and probably more.
The principle I took to begin with, and w ork upon, was that the small segment of a large circle was preferable to the great segment of a small circle. The appearance of such arches, and the manner of forming and putting the parts together admit of many varieties; but the principle will be the same in all. The architects I conversed with in England denied the principle, but it was generally supported by mathematiciaus, and experiment has now established the fact .
In 1786 I made three models, partly at Philadelphia, but mostly at Bordentown in the State of Jersey. One model was in wood, one in cast iron, and one in wrought iron connected with blocks of wood, representing cast iron blocks, but on the same principle as that of the small segment of a large circle.
I took the last mentioned one with me to France in 1787, and presented it to the Academy of Sciences at Paris, for their opinion of it. The Academy appointed a committee of three of their own body—Mons. Le Roy, the Abbe Bossou, and Mons. Borde. The first was an acquaintance of Dr. Franklin, and of Mr. Jefferson, then minister at Paris. The two others were celebrated as mathematicians. I presented it as a model for the bridge of a single arch of four hundred feet span over the river Schuylkill at Philadelphia. The committee brought in a report which the Academy adopted—that an arch on the principle and construction of the model, might, in their opinion, be extended four hundred feet, the extent proposed.
In September of the same year, I sent the model to Sir Joseph Banks, President of the Royal Society in England, and soon after went there myself.
In order to ascertain the truth of the principle on a larger scale than could be shewn by a portable model of five or six feet in length, I went to the iron foundery of Messrs. Walkers', at Rotheram in the county of Yorkshire, in England, and had a complete rib of ninety feet span, and five feet of height from the cord line to the centre of the arch, manufactured and erected. It was a segment of a circle of four hundred and ten feet diameter; and until this was done, no experiment on a circle of such extensive diameter had ever been made in architecture, or the practicability of it supposed.
The Rib was erected between a wall of a furnace belonging to the iron works, and the gable end of a brick building, which served as butments. The weight of iron in the rib was three tons, and we loaded it with double its weight in pig iron. I wrote to Mr. Jefferson, who was then at Paris, an account of this experiment; and also to Sir Joseph Banks in London, who in his answer to me says—" I look for many other bold improvements from your countrymen, the Americans, who think with vigour, and are not fettered with the trammels of science before they are capable of exerting their mental faculties to advantage."
On the success of this experiment, I entered into an agreement with the iron founders at Rotheram to cast and manufacture a complete bridge, to be composed of five ribs of one hundred and ten feet span, and five feet of height from the cord-line, being a segment of a circle of six hundred and ten feet diameter, and to send it to London to be erected as a specimen for establishing a manufactory of iron bridges to be sent to any part of the world.
The bridge was erected at the village of Paddington near London, but being on a plain field where no advantage could be taken of butments without the expense of building them, as in the former case, it served only as a specimen of the practicahility of a manufactory of iron bridges. It was brought by sea, packed in the hold of a vessel, from the place where it was made; and after standing a year was taken down without injury to any of its parts, and might be erected any where else.
At this time my bridge operations became suspended. Mr. Edmund Burke published his attack on the French revolution and the system of representative government and in defence of government by hereditary succession, a thing which is in its nature an absurdity because it is impossible to make wisdom hereditary; and therefore, so far as wisdom is necessary in government, it must be looked for where it can be found. Sometimes in one family; sometimes in another. History informs us that the son of Solomon was a fool. He lost ten tribes out of twelve.* There are those in later times who lost thirteen.
The publication of this work of Mr. Burke, abused in its principles and outrageous in its manner, drew me, as I have said, from my bridge operations, and my time because employed in defending a system then established and operating in America and which I wished to see peaceably adopted in Europe—I therefore ceased my work on the bridge to em
* 2 Chron. chap. 10.
ploy myself on the more necessary work, Rights of Man, in answer to Mr. Burke.
In 1793, a Convention was elected in France, for the express purpose of forming a constitution on the authority of the people, as had been done in America, of which Convention I was elected a member. I was at that time in England, and new nothing of my being elected till the arrival of the person who was sent officially to inform me of it.
During my residence in France, which was from 1792, to 1802, an iron bridge of two hundred and thirty-six feet span, and thirty-four of height from the cord line, was erected over the river Wear, at the town of Sunderland, in the county of Durham in England. It was done chiefly at the expense of the two members of Parliament for that county, Milhanke and Burdon.
It happened that a very intimate friend of mine, Sir Robert Smyth (who was also an acquaintance of Mr. Monroe, the American minister, and since of Mr. Livingston) was then at Paris. He had been colleague in Parliament with Milhanke, and supposing that the persons who constructed the iron bridge at Sunderland had made free with my model, which was at the iron works where the Sunderland bridge was cast, he wrote to Milhanke on the subject, and the following is that gentleman's answer:—
"With respect to the bridge over the river Wear at Sunderland, it certainly is a work well deserving admiration both for its structure and utility, and I have good grounds for saying, that the first idea was suggested by Mr. Paine's bridge exhibited at Paddington. What difference there may be in some part of the structure, or in the proportion of wrought and cast iron, I cannot pretend to say, Burdon having undertaken to build the bridge, in consequence of his having taken upon himself whatever the expence might be beyond between three and four thousand pounds (sterling) subscribed by myself and some other gentlemen. But whatever the mechanism might be it did not supersede the necessity of a center.* [The writer has here confounded a center with a scaffolding.] Which center (continues the writer) was esteemed a very ingenious piece of workman
* It is the technical term, meaning the boards and timbers which form the arch upon which the permanent materials are laid: when a bridge is finished, the workmen they say are ready to strike the centre, that is to. take down the scaffolding.
ship, and taken from a plan sketched out by Mr. Nash, an architect of great merit, who had been consulted in the outset of the business when a bridge of stone was in contemplation.
"With respect, therefore, to any gratuity to Mr. Paine, though ever so desirous of rewarding the labour of an ingenious man, I do not feel, how, under the circumstances already described, I have it in my power, having had nothing to do with the bridge after the payment of my subscription. Mr. Burdon then becoming accountable for the whole. But if you can point out any mode, according to which it should be in my power to be instrumental in procuring him any compensation for the advantage the public may have derived from his ingenious model, from which certainty the outline of the bridge at Sunderland was taken, be assured it will afford me very great satisfaction *
The year before I left France, the Government of that country had it in contemplation to erect an iron bridge over the river Seine at Paris. As all edifices of public construction came under the cognizance of the Minister of the Interior—(and as their plan was to erect a bridge of five iron arches of one hundred feet span each, instead of passing the river with a single arch, and which was going backward in practice, instead of forward, as there was already an iron arch of two hundred and thirty-six feet in existence) I wrote the Minister of the Interior, the Citizen Chaptal, a memoir on the construction of iron bridges. The following is his answer:—
The Minister of the Interior to the Citizen Thomas Paine.
I have received, Citizen, the observations that you have been so good as to address to me upon the construction of iron bridges. They will be of the greatest utility to us in a moment when this new kind of construction goes to be executed for the first time. I see with pleasure, Citizen, that you have rights of more than of one kind to the thankfulness of nations, and I give you, cordially, the particular expression of my esteem .t
* The original is in my possession.
t The original in French is in my possession.