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Antique French Folding Brass sector,c.18th century


Offered for sale is an 18th century Antique French folding/hinged Brass sector, engraved Mre. du Pied and Mre. du Metre, meaning inches and meters, and made in France dating from the 18th century, with scales for lines of equal parts, polygons, line of chords, metals, weights of shot and gun caliber. Unlike the English sectors, which were used for general calculation, the French ones were generally intended for gunnery calculations.

The instrument measuring 15 meters and six inches, is in polished brass and with rosette-engraved joint, is in well preserved condition.

The instrument has scales for lines with equal parts, with integrated plum bob, and has the facility for a plum bob line on one side and the traditional "Cut Arch" so when that side was set plum, the other side would then be level. This instrument is a square rule ~ plum with various tables for measurements.

Galileo Galilei (1564-1642) Popularized the sector at the very end of the 16th Century. The sector is a graduated ruler that uses trigonometric formulae and a caliper to calculate squares, cubes, reciprocals and tangents of numbers. Galileo's design of the sector as a mathematical tool can be seen as the moment when calculation aids cease to be based upon counting and instead exploit the deeper relationships among numbers. His invention is still in use as a navigation aid in the 20th century 300 years later.(ref: Oughtred Society) Sectors were frequently included in sets of drawing instruments in the eighteenth and nineteenth centuries until made obsolete by the slide rule. There are three types of scale on an English sector: sectoral ones (radiating from the hinge centre), which were used for calculation; plane scales (logarithms, sines, tangents) parallel to the edge; and rules (inches, tenths of feet). Most were six inches in length.

French Sector: Made in France. A brass sector dating from the eighteenth century with scales for line of equal parts, polygons, line of chords, metals, weights of shot and gun calibre. Unlike English sectors, which were used for general calculation, the French ones were generally intended for gunnery calculations.

Of the three main styles, French sectors were the most consistent in terms of the scales with which they were marked. They were designed specifically for gunnery rather than for general applications. There were eight common scales: •Poid des boulets, or weight of artillery shot – Although early modern cannon were not standard in size, there were different types of shot for different general types of artillery. Each type of shot had a particular volume, weight, and amount of powder. This scale helped gunners determine the required weight for a given size of shot. •Metallic line – The alchemical symbols for certain metals (such as gold, lead, silver, copper, iron, and tin) were placed at distances from the hinge of the sector so that balls of those metals with those radii would weigh the same. The distance between any two metals gave the ratio between their weights. •Line of solids – Used to determine the ratio between two volumes and to calculate cube roots. •Line of chords – Used to construct angles. •Calibre des pieces, or size of artillery shot – This scale was used to determine the size of shot, given the diameter of the cannon opening and the weight of the shot. •Line of lines – A scale divided into equal parts used as the base scale for taking measurements that are transferred to other scales with a pair of dividers. For example, open the dividers to a length on the line of lines and then pivot the dividers and open the sector so that the lifted point of the dividers falls on the other leg of the sector. •Line of planes – Used to determine the ratio between two areas and to calculate square roots. •Tetragonic line – Points placed from the hinge to represent the sides of regular polygons with the same area, from the triangle to a 13-sided polygon. Used to set up proportions to determine the areas of regular polygons with other side lengths.

Ref: Antique Scientific Instruments, by John Fitzmaurice Mills, Aurum Press Scientific Instruments of the 17th & 18th Centuries & Their Makers, by Maurice Daumas, Portman Press. The Charles Babbage Institute. Handbook of the Napier Tercentenary. Modern Instruments, Books, & Devices for facilitating Methods of Calculation. By E. M. Horsburgh, Thomas Publication. The original edition, 1914 by G. bell & Sons, Ltd., and the Royal Society of Edinburgh.

Shipping: FREE to the United States. We also will ship worldwide.

Please look at the picture and read the description, which form a part of the condition description. What you see and what you read is what you are buying

International purchasers should contact sellers at: CAPTAINMADISON@ATT.NET for a shipping and insurance quote to your address and country. International purchasers should appreciate that the Customs Dept. of your country may assess duties, taxes and/or other charges on your purchase as it enters your country, which expenses are not part of the purchase price for this item and remains the sole expense of the purchaser.

This product would make a wonderful addition to any scientific instrument or sundial collection when displayed in a prominent place, being a grand collectible item that would adorn any serious collector's prized scientific instrument and sundial accumulations, while showing a discriminating dedication for fine sundials and other scientific instrument items as well as a devotion to acquiring fine collectibles.

Sellers exclusively use the USPS as its' shipper (insurance available).

Please email sellers to: CAPTAINMADISON@ATT.NET for purchasing, payment, shipping arrangements, requests for more photos, as well as any other inquiries.

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  • Model: French Folding Sector

This product was added to our catalog on Monday 10 March, 2014.

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