1875s Brass Sextant Signed Negus New York Antique Marine Navigation Instrument

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1875s Brass Sextant Signed Negus New York Antique Marine Navigation Instrument

About the Item

Brass sextant signed Negus New York, datable around 1875, finely manufactured instrument, complete with optics and housed in an elegant original square wood box with closing hooks and lock with brass key. Brass frame with engraved silver protractor scale recessed in the arch, with scale from, silver flap and vernier, wooden handle, 3 colored glasses for the fixed mirror and 4 for the mobile one, three telescopes, a microscope for reading the vernier, index and horizon mirror. State of conservation: excellent, complete with support base made of wood and custom-made brass. Box measures 27 x 26.5 h 12.7 cm – 10.6 x 10.45 x 5 inches Our gift box is free (look at the last picture). The brothers Thomas Stewart and John D. Negus were highly regarded nautical instrument makers and arguably the leading manufacturers in the United States during the second half of the 19th century. They moved to New York City in 1864 and formed their own navigation instrument company, "TS & JD Negus", in 1869. In 1886 the United States Navy conducted one-year sea trials testing 47 chronometers, of the twelve accepted , 8 belonged to the Negus brothers, after this resounding success The company continued under the trade name "Negus" as both a manufacturer and retailer of nautical instruments well into the 20th century. The sextant is an optical instrument used in astronomical navigation to measure the height of the stars above the horizon, in order to obtain the geographic coordinates relative to the ship's point. It has the shape of a circular sector of 60, i.e. one sixth of a circumference, hence the name, at whose vertex a mobile alidade is pivoted on which a mirror is fixed which rotates with it. On the back of the mirror there is a support with a telescope oriented towards a second mirror, only half silvered, which allows you to observe the marine horizon at the same time, in alignment, and the pointed star, whose image is reflected by the fixed mirror to the alidade and subsequently from the silver side of the mirror. Was Sir Isaac Newton who invented the principle of double reflection in navigation instruments, but this research was never published. Subsequently, two men independently discovered the sextant around 1730 John Hadley (1682 - 1744), English mathematician, and Thomas Godfrey, (1704 - 1749), American inventor. But it was only in 1758 that Admiral John Campbell carried out a series of tests in the open sea to experiment with a new method which relied on the lunar distance as a means of calculating longitude. This is how the sextant was developed. Initially produced in brass, they had scales divided with great precision by mathematicians who made scientific instruments.

Dimensions:
Height: 5 in (12.7 cm)Width: 10.45 in (26.55 cm)Depth: 10.6 in (26.93 cm)
Materials and Techniques:
Brass
Period:
1870-1879
Date of Manufacture:
1875
Condition:
Seller Location:
Milan, IT
Reference Number:
1stDibs: LU1020234231982