Thomas Paine (1737–1809). The Writings of Thomas Paine. 1906.
IX.Specification of Thomas Paine
Constructing Arches, Vaulted Roofs, and Ceilings.
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The idea and construction of this arch is taken from the figure of a spider’s circular web, of which it resembles a section, and from a conviction that when nature empowered this insect to make a web she also instructed her in the strongest mechanical method of constructing it.
Another idea, taken from nature in the construction of this arch, is that of increasing the strength of matter by dividing and combining it, and thereby causing it to act over a larger space than it would occupy in a solid state, as is seen in the quills of birds, bones of animals, reeds, canes, etc. The curved bars of the arch are composed of pieces of any length joined together to the whole extent of the arch, and take curveture by bending. Those curves, to any number, height, or thickness, as the extent of the arch may require, are raised concentrically one above another, and separated, when the extent of the arch requires it, by the interposition of blocks, tubes, or pins, and the whole bolted close and fast together (the direction of the radius is the best) through the whole thickness of the arch, the bolts being made fast by a head pin or screw at each end of them. This connection forms one arched rib, and the number of ribs to be used is in proportion to the breadth and extent of the arch, and those separate ribs are also combined and braced together by bars passing ’cross all the ribs, and made fast thereto above and below, and as often wherever the arch, from its extent, depth, and breadth, requires. When this arch is to be applied to the purpose of a bridge, which requires more arches than one, they are to be connected in the following manner (that is to say):—Wood piles are to be driven into the earth; over each of those piles are to be let fall a hollow iron or metal case, with a broad foot let into a bed; the interspace between the case and the wood pile to be filled up with a cement and pinned together. The whole number of those pillars are to be braced together, and formed into a platform for receiving and connecting the arches. The interspaces of those pillars may be filled with plates of iron or lattice work so as to resemble a pier, or left open so as to resemble a colonade of any of the orders of architecture. Among the advantages of this construction is that of rendering the construction of bridges into a portable manufacture, as the bars and parts of which it is composed need not be longer or larger than is convenient to be stowed in a vessel, boat, or waggon, and that with as much compactness as iron or timber is transported to or from Great Britain; and a bridge of any extent upon this construction may be manufactured in Great Britain and sent to any part of the world to be erected. For the purpose of preserving the iron from dust it is to be varnished over with a coat of melted glass. It ought to be observed, that extreme simplicity, though striking to the view, is difficult to be conceived from description, although such description exactly accords, upon inspection, with the thing described. A practicable method of constructing arches to several hundred feet span, with a small elevation, is the desideratum of bridge architecture, and it is the principle and practicability of constructing and connecting such arches so as totally to remove or effectually lessen the danger and inconvenience of obstructing the channell of rivers, together with that of adding a new and important manufacture to the iron works of the nation, capable of transportation and exportation, that is herein described. When this arch is to be applied to the purpose of a roof and ceiling cords may be added to the arch to supply the want of butments, which are to be braced to or connected with the arch by perpendiculars.
stamped, in the presence of
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Inrolled the said Twenty-fifth day of September, in the year last above written.