LORIEUX LEPETIT. Brass hydrographic circle. Brass Alidade. B - Lot 110

Lot n° 110
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Estimation :
600 - 900 EUR
LORIEUX LEPETIT. Brass hydrographic circle. Brass Alidade. B - Lot 110
LORIEUX LEPETIT. Brass hydrographic circle. Brass Alidade. Blade and vernier divided on silver. Turned wooden handle. Complete with its optics, large and small mirror, filters, magnifying glass for angle measurement. Signed and engraved "LORIEUX LEPETIT Suc. Paris" on the arc of limbus. Alidade engraved "SH 141" for "Service Hydrographique, instrument scientifique référencé 141". Varnished mahogany case with accessories. Brass identification plate on the lid of the box engraved: "Service Hydrographique - Cercle Hydrographique - LORIEUX LEPETIT Suc. Paris - N° 141". Diameter of the circle 26.5 cm. Box: 31.5 x 31.5 cm. Sold as is. Note: Octants, sextants, reflection circles, also called Borda circles, are angle measuring tools. They make it possible to aim simultaneously at the two directions whose angle is to be measured. The reading of the angle is done on a circle, so it can then be measured angles of 360° or on a portion of a circle. 1/8th of a circle is 45° for an octant - 1/6th of a circle or 60° for a sextant. The various constituent parts of these instruments evolved over time. The mahogany or ebony body or frame on the first octants was replaced by brass. Single frame or double frame. The pinnacle sight was replaced by the telescopic sight. Ivory limbo then silver limbo. The verniers, reading magnifiers, adjustment system by simple screw then micrometric drum. Note: Heir to the first hydrographic service in the world created in 1720 under the name "Dépôt des cartes et plans de la Marine", it became "Service hydrographique de la Marine" in 1886.
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