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J. Sifson 6" Equinoctial Ring Dial
[Text discription below]
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50015
A Rare 6 Inch, Universal Equinoctial Ring Dial with Case:
English ca. 1725. Signed: “J·Sifson · London”. A supreme example of William Oughtred’s Universal Equinoctial Ring Dial invention first published in 1652. Although published in 1652, the actual design and use of this type of dial seems to date to the mid 1630’s since early examples by Elias Allen are known, and appear to be the result of some collaboration by the two (2). This dial features the Sifson’s absolutely superlative engraving throughout, including wheat-leaf borders, indicating membership to the London trade guilds. Made of brass and blued steel screws, the dial is suspended by a 32 mm Ring and a 32 X 22 mm Shackle. The overall diameter is 6.25 inches, excluding shackle.; i.e. 160 X 4 mm. Weight is 453.4 g.
J Sifson (1) refers to Jeremiah or Jonathan Sifson (or Sisson), London Scientific Instrument makers working between 1722-1780 in the Strand. Jonathan Sifson (w 1722-1737) was the father of Jeremiah Sifson (w 1749-1780) who passed the business on to his son. The present dial has the vernal equinox set to March 9th, indicating that the dial was made pre 1752, the date the Gregorian Calendar (3) was adapted in GB. The March 9th vernal equinox is consistent with a Julian Calendar date of 1725 (4). Little is known about how to differentiate instruments made by the father and son, and any type of separation of attributes may not be possible for instruments emanating from the same workshop. The present dial has the maker’s signature in gothic, while many other Sifson instruments, such as rules and sectors, have the signature J Sifson in script.
The sliding ring on the circumference of the meridian ring to which the suspension assembly/schackle is attached, is connected at the bottom in halves via a single steel screw. This type of attachment by itself is extremely rare. Search of the databases of the NMM (National Maritime Museum, Greenwich) and the MHS (Museum of The History of Science, Oxford) and the Adler Planetarium, Chicago, reveals only one other example of a ring dial connected by this method. That is the ring dial by Thomas Wright (w 1714-1748) (Inventory #86833; MHS). This early example suggests a parallel in construction methodology for the time, possibly concluding that Jonathan Sifson may be the most likely maker. This is certainly consistent with a manufacture date within his working life, i.e. ca. 1722-1737, in keeping with a vernal equinox date of March 9th in 1725. The Horary Fascia:
The inner ring, also called the equinoctial ring, is hinged by two brass pins placed 180 degrees apart. When the instrument is opened, the equinoctial ring represents the celestial equator of the Earth. This ring features an engraved black-waxed Roman Numeral Horary Scale of 24 equal parts, i.e. I-XII hours twice, through 360 degrees, thus being a 24 hour calibration. The inner edge is also finely calibrated so that the time, indicated by the sun’s fine pin-beam projected through the Bridge’s pinhole gnomon, can be read along the inner edge.
The outer ring, also called the meridian ring, is divided into 4 X 90 degree quadrants with a North-South 90 degree locking bracket (20 X 18 mm) which sets the hinged inner ring at right angles to the Outer Ring when in use. The meridian ring represents a giant circle passing through the North and South celestial poles.
There is a 160 mm diameter outer brass circumference clasp-ring of 3 mm section joined by a single screw clamp.
The reverse fascia features a 0-90 degree Nautical Quadrant Scale for measuring the altitude of the sun, with a 30 X 20 mm shoulder bracket which sets the inner Horary Ring at 90 degrees when opened. The Bridge:
This measures 112 X 26 mm and pivots within the Inner Horary Circle, and represents the axis of the Earth. The inner sliding Pinhole Gnomon (28 X 8 mm) is adjustable for months of the year on one face with 2 day subdivision rulings.
The reverse features an upper scale of South Declination (S·D), Celestial Equator (Æ) and North declination (N·D). Below, a Zodiacal Symbol Scale for positioning the Pinhole gnomon according to the current celestial zodiac sign. Condition:
This dial has survived in absolutely untouched condition over the centuries, preserved within its original fish-skin covered wooden case (175 mm X 20 mm) with one hinge, and three original brass hooks and eye catches. The interior, as new, reveals a green plush velvet lining and the case borders colored red, typical of early 18th century English instrument cases. A very early and rare dial, near impossible to find in this conditon. A legendary find from a legendary scientific instrument dealer. Provenance: Stewart Talbot
Bibliography:
1. Clifton, Gloria (1995). Directory of British Scientific Instrument Makers 1550-1851, IBSN [0 302 00634 6] p. 253. 2. Higton, Hester ( 2001) Sundials, An Illustrated History of Portable Dials, ISBN [0 85667 523 7] p. 77-84. 3. The Gregorian Calendar, was introduced by Pope Gregory XIII in Feb 1582, but not adapted in Great Britain until Sep 1752. This established a Vernal Equinox date of Mar 21. 4. For a list of the vernal equinox dates for 1452-1811, please see: [http://ns1763.ca/equinox/vern1452-1811.html]. 5. There is a 7.5 in. J. Sisson equinoctial ring dial in the Metropolitan Museum of Art, NY (Inventory #03.21.7) made of brass and signed: I Sifson Fecit. This is most likely a 6 in. dial with the measurement taken including the shackle. 6. Jonathan Sifson's trade card is reproduced here, for use in this forum, by permission from the British Museum.
A Rare 6 Inch, Universal Equinoctial Ring Dial with Case:
English ca. 1725. Signed: “J·Sifson · London”. A supreme example of William Oughtred’s Universal Equinoctial Ring Dial invention first published in 1652. Although published in 1652, the actual design and use of this type of dial seems to date to the mid 1630’s since early examples by Elias Allen are known, and appear to be the result of some collaboration by the two (2). This dial features the Sifson’s absolutely superlative engraving throughout, including wheat-leaf borders, indicating membership to the London trade guilds. Made of brass and blued steel screws, the dial is suspended by a 32 mm Ring and a 32 X 22 mm Shackle. The overall diameter is 6.25 inches, excluding shackle.; i.e. 160 X 4 mm. Weight is 453.4 g.
J Sifson (1) refers to Jeremiah or Jonathan Sifson (or Sisson), London Scientific Instrument makers working between 1722-1780 in the Strand. Jonathan Sifson (w 1722-1737) was the father of Jeremiah Sifson (w 1749-1780) who passed the business on to his son. The present dial has the vernal equinox set to March 9th, indicating that the dial was made pre 1752, the date the Gregorian Calendar (3) was adapted in GB. The March 9th vernal equinox is consistent with a Julian Calendar date of 1725 (4). Little is known about how to differentiate instruments made by the father and son, and any type of separation of attributes may not be possible for instruments emanating from the same workshop. The present dial has the maker’s signature in gothic, while many other Sifson instruments, such as rules and sectors, have the signature J Sifson in script.
The sliding ring on the circumference of the meridian ring to which the suspension assembly/schackle is attached, is connected at the bottom in halves via a single steel screw. This type of attachment by itself is extremely rare. Search of the databases of the NMM (National Maritime Museum, Greenwich) and the MHS (Museum of The History of Science, Oxford) and the Adler Planetarium, Chicago, reveals only one other example of a ring dial connected by this method. That is the ring dial by Thomas Wright (w 1714-1748) (Inventory #86833; MHS). This early example suggests a parallel in construction methodology for the time, possibly concluding that Jonathan Sifson may be the most likely maker. This is certainly consistent with a manufacture date within his working life, i.e. ca. 1722-1737, in keeping with a vernal equinox date of March 9th in 1725. The Horary Fascia:
The inner ring, also called the equinoctial ring, is hinged by two brass pins placed 180 degrees apart. When the instrument is opened, the equinoctial ring represents the celestial equator of the Earth. This ring features an engraved black-waxed Roman Numeral Horary Scale of 24 equal parts, i.e. I-XII hours twice, through 360 degrees, thus being a 24 hour calibration. The inner edge is also finely calibrated so that the time, indicated by the sun’s fine pin-beam projected through the Bridge’s pinhole gnomon, can be read along the inner edge.
The outer ring, also called the meridian ring, is divided into 4 X 90 degree quadrants with a North-South 90 degree locking bracket (20 X 18 mm) which sets the hinged inner ring at right angles to the Outer Ring when in use. The meridian ring represents a giant circle passing through the North and South celestial poles.
There is a 160 mm diameter outer brass circumference clasp-ring of 3 mm section joined by a single screw clamp.
The reverse fascia features a 0-90 degree Nautical Quadrant Scale for measuring the altitude of the sun, with a 30 X 20 mm shoulder bracket which sets the inner Horary Ring at 90 degrees when opened. The Bridge:
This measures 112 X 26 mm and pivots within the Inner Horary Circle, and represents the axis of the Earth. The inner sliding Pinhole Gnomon (28 X 8 mm) is adjustable for months of the year on one face with 2 day subdivision rulings.
The reverse features an upper scale of South Declination (S·D), Celestial Equator (Æ) and North declination (N·D). Below, a Zodiacal Symbol Scale for positioning the Pinhole gnomon according to the current celestial zodiac sign. Condition:
This dial has survived in absolutely untouched condition over the centuries, preserved within its original fish-skin covered wooden case (175 mm X 20 mm) with one hinge, and three original brass hooks and eye catches. The interior, as new, reveals a green plush velvet lining and the case borders colored red, typical of early 18th century English instrument cases. A very early and rare dial, near impossible to find in this conditon. A legendary find from a legendary scientific instrument dealer. Provenance: Stewart Talbot
Bibliography:
1. Clifton, Gloria (1995). Directory of British Scientific Instrument Makers 1550-1851, IBSN [0 302 00634 6] p. 253. 2. Higton, Hester ( 2001) Sundials, An Illustrated History of Portable Dials, ISBN [0 85667 523 7] p. 77-84. 3. The Gregorian Calendar, was introduced by Pope Gregory XIII in Feb 1582, but not adapted in Great Britain until Sep 1752. This established a Vernal Equinox date of Mar 21. 4. For a list of the vernal equinox dates for 1452-1811, please see: [http://ns1763.ca/equinox/vern1452-1811.html]. 5. There is a 7.5 in. J. Sisson equinoctial ring dial in the Metropolitan Museum of Art, NY (Inventory #03.21.7) made of brass and signed: I Sifson Fecit. This is most likely a 6 in. dial with the measurement taken including the shackle. 6. Jonathan Sifson's trade card is reproduced here, for use in this forum, by permission from the British Museum.
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