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Antique J.Dale Universal Equinoctial Ring Dial


Offered for sale is a very old antique brass Universal Equinoctial Ring Dial, made by J. Dale, being 1 5/8" in diameter (4.1 cm) in very fine condition. This ring dial has a scale from 1-6 and 6-10 engraved on the inside of the brass ring, and the months of the calendar from January to December on the outside.#045

Provenance: Christie's So. Kensington, June 1992

Sellers exclusively use the United States Postal Service. Shipping domestically is FREE. We ship worldwide.

Please look at the photo as what you see and read is what you are buying. Please email sellers for questions, request for ore photos, shipping arrangements, as well as any other inquiries.

Universal Ring Dial: The dial is suspended from the cord shown in the upper left; the suspension point on the vertical meridian ring can be changed to match the local latitude. The center bar is twisted until a sunray passes through the small hole and falls on the horizontal equatorial ring.

A universal equinoctial ring dial (sometimes called a ring dial for brevity, although the term is ambiguous) is a portable version of an armillary sundial, or was inspired by the mariner's astrolabe. It was likely invented by William Oughtred around 1600 and became common throughout Europe.

In its simplest form, the style is a thin slit that allows the sun's rays to fall on the hour-lines of an equatorial ring. As usual, the style is aligned with the Earth's axis; to do this, the user may orient the dial towards true North and suspend the ring dial vertically from the appropriate point on the meridian ring. Such dials may be made self-aligning with the addition of a more complicated central bar, instead of a simple slit-style. These bars are sometimes an addition to a set of Gemma's rings. This bar could pivot about its end points and held a perforated slider that was positioned to the month and day according to a scale scribed on the bar. The time was determined by rotating the bar towards the sun so that the light shining through the hole fell on the equatorial ring. This forced the user to rotate the instrument, which had the effect of aligning the instrument's vertical ring with the meridian.

When not in use, the equatorial and meridian rings can be folded together into a small disk.

In 1610, Edward Wright created the sea ring, which mounted a universal ring dial over a magnetic compass. This permitted mariners to determine the time and magnetic variation in a single step.

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

Elizabethan Instrument Makers, by Gerard L' E. Turner, Oxford University Press

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.

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.

Payments may be made by check (must clear), bank checks, postal or bank money orders, Western Union money transfers, pre-payment arrangements, good old U.S. Dollars (green currency), and/or other secure money transfers or payments.

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  • Model: J.Dale Univ.Equi. Ring Dial

This product was added to our catalog on Sunday 27 July, 2014.

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