File:Galileo, his life and work (1903) (14580148127).jpg

Identifier: galileohislifewo00fahi (find matches)
Title: Galileo, his life and work
Year: 1903 (1900s)
Authors: Fahie, J. J. (John Joseph), 1846-1934
Subjects: Galilei, Galileo, 1564-1642 Astronomy Astronomers
Publisher: London, J. Murray
Contributing Library: Wellesley College Library
Digitizing Sponsor: Boston Library Consortium Member Libraries

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is now called the Sector,and is to be found in most cases of mathematicalinstruments. It consists of two straight rulersconnected by a joint so that they can be set toany required angle. On one face are four pairsof lines. Arithmetical lines, which serve for the divisionof lines, the solution of the Rule of Three, theequalisation of money, the calculation of interest. Geo77ietrical lines, for reducing proportionallysuperficial figures, extracting the square root,regulating the front and flank formations ofarmies, and finding the mean proportional. Stereometrical lilies, for the proportional reduc-tion of similar solids, the extraction of the cuberoot, the finding of two mean proportionals, and forthe transformation of a parallelepiped into a cube. ^ So sayViviani and Gherardini in their biographies of Galileo, butProfessor Favaro, after a diligent search among the archives of \enice,could find nothing to bear out the statement. For this and othercogent reasons he doubts its accuracy.
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■<, ^ i6io) GEOMETRICAL COMPASS 43 Metallic lines, for finding the proportionalweights of metals, and other substances, for trans-forming a given body into one of another materialand of a given weight. On the other side of the instrument are : Polygraphic lines, for describing regularpolygons, and dividing the circumference intoequal parts. Tetragonical lines, for squaring the circle orany other regular figure, for reducing severalregular figures to one figure, and for transformingan irregular rectilineal ficrure into a regfular one. Joined lines, used in the squaring of the variousportions of the circle and of other figures containedby parts of the circumference, or by straight andcurved lines together. There is joined to the compass a quadrant,which, besides the usual divisions of the astro-nomical compass, has engraved on it a squadronof bombardiers, and, in addition, transversal lines,used for taking the inclination of a scarp of a wall. From the encouraging reception given t

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