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Antique Universal Equinoctial Ring Dial


Offered for sale is an Antique Universal Equinoctial Ring Dial in outstanding condition. The Universal Equinoctial Ring Dial is 2 1/2'" in diameter. The Ring Dial is divided into sectors, South 90 degrees to North 90 degrees, and divided into Months, and further calibrated into 24 hours, with an adjustable Calendar calibrated into 12 Months. This outstanding brass universal equinoctial ring dial, the meridian ring divided 90 - 0 70. The pivoted equinoctial ring with I - XII hours scale (x2), the bridge with sliding pin hole sight against calendric, zodiac and declining scales (6.3cm) diameter.

Hinged meridian ring with latitude scale, equinoctial ring with Roman numerals and hatch index, bridge bar with peep sight and calendar. The meridian ring with N and S flanking the zero line on the latitude scale and calibrated 0-90, the equinoctial ring engraved with Roman numeral hours, the central bridging bar with sliding peep hole engraved with the months, all suspended by a brass ring. We believe the genealogy is London England.

Literature: Gloria Clifton, Directory of British Scientific Instrument Makers, 1550-1851.

Technical description of a Universal Ring Dial: This type of portable dial is called universal because it is adjustable for use in any latitude. Pivoted across the center of the outer ring is a thin metal "bridge". The bridge is slotted and bears a cursor pierced with a tiny hole. The cursor is moved to that point on the bridge which corresponds to the day of the observation. The Sun shining through the tiny hole casts a beam of light on the inner surface of the time ring, which is calibrated to show the hours of the day,

To use the dial, adjust the suspension ring to the correct latitude, using the upper scale if one is at the northern hemisphere and the lower scale if one is at the southern hemisphere. Next, slide the cursor on the bridge to the correct date. Then, put the hour ring 90 degrees down until it touches the stoppers. Then hold the sundial on the string or ring and turn it slowly until a sun ray hits the notch on the hour ring. Now you can tell the local time. If applied correctly, the outer ring will now be aligned in the north-south direction, the hour ring will be parallel to the equator and the bridge with the cursor will be parallel to the axis of the earth.

History of the Equinoctial Ring Dial: The universal equinoctial ring dial was developed from the astronomer's ring which was first mentioned by Gemma Frisius and other 16th century authors. Described as 'a simplified armillary sphere consisting of three or four rings, with pinhole sights', the astronomer's ring was used for measuring altitudes of stars and terrestrial objects. A two-ring dial (far more common than a three-ring dial) soon developed from this type of instrument. This replaced the innermost ring with a bridging bar containing a central slot, in which a sliding pinhole sight could move along a date scale. This instrument was designed by the English mathematician, William Oughtred, in the first half of the 17th century. Early versions carried only a date scale on the bridge and were normally for use in northern latitudes alone. Towards the end of the 17th century, zodiac and solar declination scales were added to the bridge and a further degree scale was supplied to allow use of the instrument in southern latitudes. At the same time, an altitude quadrant appeared on the back, which was used for measuring heights, in conjunction with a stylus set in a hole in the back of the instrument. These adjustments made the universal equinoctial ring dial a particularly suitable dial for use at sea.

Provenance: Christies, Sept. 1992 auction.

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

Shipping to the Continental United States is FREE. 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.

Please look at the photos and read the description as what you see and read is what you are buying.

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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: Universal Equinoctial Ring Dial

This product was added to our catalog on Tuesday 16 September, 2014.

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