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An exceptional and rare set of Brass Sector and Diagonal Scale. 18th Century Made by Heath & Wing, London. The sector is engraved with scales of mathematical functions (to give similar information to that provided by a slide rule): Line of Sinus, 0° - 90°. Line of Tangents 0° - 45° - 75°. Line of Chords 0° - 60° to protract an angle. Line of Latitude 0° - 90° and line of Hours 0 - VI of sundial. 18th cent. |
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