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7. Archimedes as Civil and Military Engineer
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59 ARCHIMEDES AS CIVIL AND MILITARY ENGINEER VII Of all the machines constructed under Archimedes’ direction , the ship Syracusia, ordered by the tyrant Hiero II in 240 BC as a token of the tyrant’s prosperous reign, occupies a special place. It was, in all likelihood, the largest vessel of antiquity, with a vast capacity estimated between 3,650 and 4,200 tons,1 a capability that would not be seen again until the nineteenth century, when iron and steel, in particular, were introduced for the construction of holds [plate 7]. A fascinating description of the Syracusia has been handed down by the third-century AD author Athenaeus in the Deipnosophistae (“Professors at Dinner”),2 a work that has only recently begun to receive adequate scholarly attention. It is preserved in a tenth-century codex of the Biblioteca Marciana in Venice, recopied many times from that source during the Renaissance. Atheneaus reports that Archimedes imagined a complex system of winches and pulleys that would allow only a few men to launch the huge boat in the sea or carry it on land [fig. 19; plate 8]. 60 THE GREAT ARCHIMEDES VII Figure 19 System of winches and pulleys (also known as Archimedes’ block and tackle) invented to move with little effort even very large weights, such as the ship Syracusia, here depicted in a reconstruction by Gian Maria Mazzucchelli in a drawing from his biography of Archimedes (Brescia: Rizzardi, 1737). [54.160.244.62] Project MUSE (2024-03-19 02:10 GMT) ARCHIMEDES AS CIVIL AND MILITARY ENGINEER 61 VII Moreover, Athenaeus reports that Archimedes carried out the scientific and technical supervision of the undertaking of the building of the ship. Upon its completion, the Syracusia was offered as a gift to the Egyptian rulers of Alexandria by the Syracusans, providing a tangible symbol of both the Sicilian city’s wealth and political sway. In a gesture suited to the occasion, Hiero changed the name of the boat to Alexandris. To keep the ship’s hold dry, Archimedes designed a large bilge pump known as the cochlea (“snail”), sometimes referred to as the “the screw of Archimedes.” This instrument, brilliant in its simplicity, was a spiral siphon consisting of a vine-like spiral running inside a cylinder with a crank that could be operated by a single sailor, possibly by foot power. The water entered from the base, itself lower than the inclined vine-like spiral, making its way upward by the revolutions of the spiral; the flow of water was continuous, so that it did not leave any more unwanted residue than had the older laborious system of buckets [plate 9]. The height to which water could be raised would have depended on the length and inclination of the device. That this kind of spiral pump could be used for industry is mentioned also by the first-century BC historian Diodorus Siculus, who describes how such a machine was used in a Spanish mine: Sometimes, deep in the earth, miners break into subterranean rivers, whose force they overcome by cutting through their supply streams with crooked ditches as those streams cascade into the rivers. Driven by the promise of gain . . . the miners draw off the streams by so-called Egyptian screws, which Archimedes of Syracuse discovered when he visited Egypt. And because of these screws, the men are continually able to transport the water up to the mine’s opening through a kind of a 62 THE GREAT ARCHIMEDES VII relay device, thereby drying up the area for mining and readying it for use. [Historical Library 5.37] Some parts of large snail-like screws from the Roman period have been found in a mine in Spain in the province of Huelva, near the coast, due west of Seville [fig. 20]. These pumps would have been of such size that a single one of them could raise the water from the bottom of a well to a height of about 10 meters. The calculations were made by modern scholars following the instructions of Vitruvius outlined in De architectura (10.6). It has been calculated that the screw could pump, for each single meter, about 200 liters of water per minute (cf. fig. 21).3 Some historians of science, however, suspect that an apparatus similar to that of Archimedes was already in use, which merely came to his notice in 243 BC during his journey in Egypt, where the instrument might have been used to pump water to irrigate the...