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HERO was a pupil of Ctesibius, with whom his name is constantly associated. By some authorities the date of hero and of Ctesibius is referred to the century preceding; and there is a very much later Hero of Alexandria, who also wrote on geodesy. Hero is the author of a collection of works bearing on the application of geometry to the arts of life, and especially on practical mensuration. Geometry had originated, so Herodotus tells us, in the difficulties created by the inundations of the Nile, when boundaries had to be resettled. Modern research has gained from Egyptian records a mathematical treatise written by Ahmes, between the seventeenth and twentieth centuries B.C. We find in it many practical rules of mensuration; but these are never demonstrated, and are not always accurate. For instance, the area of an isosceles triangle is taken as half the rectangle formed by the base and one of the sides. Egyptian geometry was strictly limited to the utilitarian purpose of measuring boundaries, and of seeing that the direction of temple walls and the sides of pyramids were true to the pole and to the points of the compass.
In Hero's hands scientific geometry, which had arisen long ago from the practical work of life, now reverted to its source. He gave the first example of the systematic application of science to industry. In finding the angles necessary for the determination of the area of a field, he used an instrument called the dioptra, the germ of the modern theodolite, consisting of a ruler pivoting on a horizontal circle, and furnished with sights. The horizontal was kept true by a water-level, the vertical support by a plummet; indeed the instrument wanted little but the telescope and the vernier to render it equal to modern appliances. It was thus possible, with the scientific laws which had now become familiar, to set out a line between two points neither of which could be viewed from the other, and fix the distance from the observer of an inaccessible point, or between any two such points; and, generally, to survey a tract of country, or to restore a boundary of which the plan existed and one or two points were known.
Hero wrote other works on the raising of weights, on projection of missiles, on the use of compressed air or steam as motive agents. No immediate result followed from these; but they illustrate the tendency of his time to bring science into contact with industry.
| This biography is
reprinted from The New Calendar of Great Men. Ed. Frederic
Harrison. London: Macmillan and Co., 1920. |
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