- Museum number
Planispheric astrolabic clock; verge escapement with balance; going-train with fusee; movement housed in drum-shaped base, linked through the pillar to drive the dials on the front; astrolabe of conventional type, womb marked for use at 51 32 (perhaps for Gottingen); rete has seventeen named star pointers, magnitudes as well as names of the stars recorded; moon globe, half black and half white, rotates about an axis and shows its phase visually; ivory topped pin passes through a slot and engages with groove in ecliptical circle of the rete, showing position of sun in ecliptical; moon's age and position also recorded; reverse: manually operated calendar dial with months in French and date.
- Production date
Diameter: 16.20 centimetres (base)
Diameter: 11.90 centimetres (vertical dial diameter)
Height: 30.70 centimetres
- Curator's comments
See 'Supplementary observations on an Astronomical and Astrological Table-clock together with an account of the astrolabe' by Octavius Morgan, 1852
The following text is the entry for this object from the unpublished catalogue of pre-pendulum clocks by John Leopold, former Assistant Keeper of Horology at the Museum. This information is unedited and should be used accordingly.
MIRROR CLOCK, 1560.
The base adapted from an earlier horizontal table clock.
Acc. to register: Formerly belonged to Dr.Hook; then in the possession of W.Finch, watchmaker of Hampstead. See Archaeologica XXXIV.16. (Then follows the ref. to Ferguson's common place book, given by Lloyd.)
Smyth (1851) 15-17 (clock said to have belonged to Dr.Hook; until recently
of "Mr. Finch, a watchmaker of Hampstead", but now Morgan's; gives picture).
Morgan (1852) 293-8.
PSA 2 (1853) 176 (meeting of 19th June 1851).
Henderson 1 (1867) 386-7 (quotes the Common Place Book of Ferguson p.136
dd. 1st Jan.1776; F. had been given the clock ca.1770 by Thomas Mudge;
Henderson did not know the actual clock).
Henderson 2 (1870) 386-7.
Postcards (1925) no.6 (thought to be French).
Lloyd (1958) 110.
Lloyd 3 (1964) Pl.3.
Lloyd (1964) 55.
Tardy 5 (1981) I 106.
Tait (1983) 31-2.
Cardinale (1986) 29-33 (noted Focard).
Aked (1986) (quotes Smith and gives his illustration).
Millburn (1988) 209-210 (ill. of the Ferguson drawing).
Panicali (1988) 82 (ascribes the clock to de la Garde!)
Wenzel (1996) 44-45.
Signed on the outside of the base with a punchmark which may be interpreted as a "W".
Case and dials.
The case and the dials are all constructed of brass, gilded on the outside (and a narrow band on the inside of the band of the base).
The lower portion of the clock, which contains the movement, is constructed like a French horizontal table clock. The band, bent out of strip and brazed at the join, is surrounded at top and bottom by two profile rings. The bottom ring is also bent out of strip and brazed at the join; the top one consists of a similar ring, to the top of which a further profile ring was brazed (this top ring appears to consist of an inner and an outer part, brazed together). All elements of the top ring were bent out of strip and brazed at the join. Both profile rings have subsequently been mutilated by turning them down in a lathe (presumably in order to add a mantle around the case); this process has exposed clear traces of the construction.
At the top of the band and resting against the underside of the profile ring is another flat ring; this ring was cut out of sheet and brazed in position. The underside of the ring shows the remains of 24 regularly spaced rivets, which are clearly remains of touch pins. The top surface of this ring is slightly dished, which seems to indicate that earlier engraving has been removed.
The base of the clock consists of a brass disc, to which a circular rim has been brazed; this rim is friction-tight to the inside of the band. The base has a winding hole (probably later) and three brass ball-feet, riveted with iron rivets. In the centre of the outside of the base is a punchmark "W"(?).
The band is engraved with twelve roundels containing representations of the twelve Signs of the Zodiac, each accompanied by its symbol and the symbol of the planet which rules that sign: Aries - Mars, Taurus - Venus, Gemini - Mercury, Cancer - Moon, Leo - Sun, Virgo - Mercury, Libra - Venus, Scorpio - Mars, Sagittarius - Jupiter, Capricorn - Saturn, Aquarius - Saturn, and Pisces - Jupiter. The symbols for Mars and Sun are somewhat unusual. The triangular portions betweem the roundels are filled with a design of stylized clouds; the roundel of Virgo has a subsquent hole to reach the regulator for the balance spring.
The horizontal ring has a primitive bead-and-reel ornament; this ornament consists of 50 parts, and therefore cannot match the 24 touchpins.
On the inside of the band two brass blocks have been brazed, each with a hole to take the latches of the movement; there are no guiding ridges.
The top of the lower portion is covered by a gilded brass disc, located by four holes that fit over extensions of the movement pillars; the disc is held in position by the bead-and-reel ring of the band. This disc is engraved with a representation of the Ptolemaic universe, in which the pillar represents the position of the Earth. The rings are marked, from the inside: "Aer" (air), "Ignis" (fire), then the symbols for Moon, Mercury, Venus, Sun, Mars, Saturn and Jupiter, then "Firmamentum" (the stellar firmament), "Cristallinum" (the Crystaline sphere) and "Primum mobile" (the Prime Mover).
A paper disk was formerly pasted to the inside of the base (now preserved separately). It has, in the handwriting of Fergusson, a description of the wheelwork and calculations of its performance. They are accurate, except that in the drive for the sun the transmission 40/5 is given as 6/48, which makes no difference to the result.
The gilded brass pillar is cast in one piece; it is hollow to take the arbor that drives the dials. The pillar is screwed to a male screw-end mounted on the movement; the female thread consists of a spiral of brass wire brazed inside the hole of the pillar.
The pillar has engraved wreaths around the base and cast egg-and-dart ornament around the capital. The main body of the pillar is punched with a table for determining the ruling planet for each hour of any weekday. It consist of seven columns: the first two, marked "HEVRE.DV IOVR" and "HEVRE.DE LA.NVICT", list the day-hours and the night-hours. The remaining seven columns list the planets in the appropriate order for each weekday; these columns are marked "DIMANCHE", "LVNDI", "MARDI", "MECREDI", "IEVDI", "VENDERD" and "SAMEDI". The first two night-hours were added to the column of day-hours in order to allow the series to break down in groups of seven planets.
The two dials are mounted on a vertical ring-shaped band, which is brazed to the pillar and contains the epicyclic astronomical gearing. The band is cast as a single piece and the profiled outer surface is engraved with palmettes. Two filled holes in the recessed middle portion, at about 4 and 8 o'clock, may be traces of ornaments since removed. At the top is a finial, the six-part pierced upper portion of which has largely broken off. The finial is pinned to the band; on the inside it secures the brass spring that takes up the slack in the drive of the epicyclic cage.
The back and its rim are cast as one piece; the inside shows traces of having been turned in a lathe. The inside of the rim is under-cut and the back may therefore originally have been a simple snap-fit to the band, but it is now secured by four small brass screws. Riveted to the centre is a steel arbor which carries the alidade with fixed sights, and extends inwards to carry epicyclic gearing and the moving elements of the dial; the pinion from which the epicyclic gearing derives its motion, forms part of this arbor.
The rim of the back is engraved with a rope-border. The back is engraved as the back of an astrolabe, surrounded by a border of accanthus leaves. The scales are: degrees (in single degrees, every fifth marked) marked 10 - 90 from the horizontal to the top and the bottom; the same scale, marked 12x 10 - 30 for the signs of the zodiac, which are named (in latin) and accompanied by their symbols; a calendar scale divided in single days and marked 12x 10 - 28/30/31, with the names of the months in French. 1. Aries = 9 March. The centre area is divided by a horizontal line. The top portion is centred by a sun, surrounded by circular scales for the Lunar Cycle (1-19), the Solar Cycle (1-28) and the Domincal Letter; these scales are flanked, on the left, by the curves for the planetary hours, and on the right by those of the Italian Hours. The bottom portion has a shadow-square divided in 12 parts, surrounded by a stellar sky with a moon. At the dentre of the square is the date 1560, engraved upside-down. For this dial see Commentary. The letters of the Dominical Cycle and all the numbers (except those of the shadow square and the date) are punched, all the rest is engraved; nearly all the markings have traces of black wax filling.
The fixed outer portion of the dial is constructed similar to the back: it is also made of a single piece, which may originally have been a snap-fit but is now held by four brass screws, and has similar decoration. This ring secures the double-sided disc of the astrolabic dial. The flat ring is engraved with a degree-scale (in single degrees, every fifth degree marked) divided on the outside in hours 2x I - XII, and on the inside in degrees 4x 10 - 90 (from the horizontal to top and bottom).
The centre portion of the dial consists of the sandwich of disc, rete, solar disc and lunar hand.
The disc is engraved on both sides with the usual coordinates, one side for 48 and the other for 5132'. The many gaps along the edge of the plate, which now serve no purpose, indicate that the metal had been used for somehting different before.
The rete is pierced in an unusual patern and shows the position of the ecliptic and 18 stars; all stars are named and their magnitude and planetary colour indicated:
The ecliptic has a groove to take the peg of the sun-immage (see later). The rete is surrounded by a ring with degree-division in single degrees with every fifth degree marked; the scale is divided 12x 10 - 30 for the signs of the Zodiac, with each sign identified by its symbol and name in latin (Libra misspelled "LIBAR"). For the design of the rete see Commentary. A steel pointer has subsequently been brazed and riveted at 1. Capricorn, to indicate syderial time on the fixed outer ring. The rete makes one revolotion in a syderial day.
Over the rete move the solar disc and the assembly of the lunar hand with revolving moon and tidal indicator. All these parts are 18th century replacements, thought to have been made by Thomas Mudge (see Provenance).
The solar disc, of gilded brass, is pierced as an aspectarium for the Moon. A small ivory bead representing sun slides in a slot of the solar dic; its position is determined by the slot of the ecliptic on the rete, which engages a brass peg at the back of the solar figure. The edge of the solar disc is divided 1 - 29 plus a small portion, to show the lunar date (in conjunction with the moon hand). The rim of the disc has a pointer at the slot for the sun-immage; this pointer indicates the date on the rete and the time on the fixed ring of the dial. The centre of the disc is pierced to form the 16 teeth that activate the revolving moon.
Over the solar disc moves the assembly of the moon hand. Like the solar disc it is an 18th century addition, and it is more elaborate than the original assembly was, for the central arbor of the dial had to be extended by means of a pinned-on pipe to accomodate all the parts. The centre of the assembly is a brass block with a square hole that fits the arbor of the moon-wheel; the block has lateral holes to reach the pin for the pipe, and carries the steel lunar hand, which is secured by two screws. The end of the hand carries the outer pivot of the revolving moon; the inner end of the arbor, with the wheel of 16 that activates the moon, is carried by the brass block. The revolving sphere of the moon is half ivory and half ebony(?).
An oval blued-steel disc is loosely riveted to the outer end of the brass block; this disc, which has four brass studs to mark the extreme positions, represents the position of high and low tide, and is to be read against the small gilded brass disc superimposed on it. The back of the disc has a stud in the centre, which is friction-tight on the brass pipe of the stationary centre arbor. The front of the disc is engraved with a projection of the Northern hemisphere, with the North Pole as the centre, and with 24 meridians (numbered 0 - 12 either way around, starting at the Prime Meridian through England). At the centre of the disc a steel screw secures the remains of a brass hand, which could be made to point at the meridian of the observer.
Plated movement, constructed largely of steel. Two circular plates separated by four profiled pillars, riveted to the back plate and pinned under the dial. There is a large aperture in the back plate near the fusee to inspect the position of the gut. All train wheels have four crossings; the three original ones have one gap between two teeth clearly marked for assembly. The second and third wheels have arbors facetted in six, the facets corresponding with the gaps between the pinion leaves; these wheels have the teeth individually marked. All holes, except those for the spring barrel, now bushed in brass.
The movement and the planet-plate slide into the case from the bottom and are secured by two sprung latches; one of the springs is extended to become the spring for the set-up click.
6 48 ║ 60 54 54
── ── ║ ── ── ── 25 (x 2)
rete ← 96 9 ║ 6 6 6
Spring barrel: brass, with traces of gilding. One cap brazed, the other dovetailed over five studs. Both caps have raised bushes. Outer end of the spring now hooked on a steel stud in the wall, but both caps retain the hole for the original cross-bar. Inner end hooked over stud on the arbor (arbor probably later). Spring not blued; 24 x .9 mm. Steel set-up wheel of 20; this wheel has been carefully repaired over distance of 5½ teeth. Subsequently a brass block was riveted to the inside of the front plate, to prevent the gut from slipping from the barrel.
Greatwheel: split fusee, cut for gut. Reversed fusee of brass; 10½ turns. The winding square and the fusee, which has an internal ratchet with a wheel of 12, are replacements, but the clickwork and the shaped crossing of the wheel suggest that the original clickwork was also internal, and the position of the stopwork shows that there always was a reversed fusee. Hinged stopwork with integral spring; the arm of the stopwork has a dovetailed and brazed arm sideways to reach the gut.
Scape wheel and arbor replaced; the wheel is of brass. Balance, staff and bridgecock are all replacements dating from the balance-spring conversion. The geared regulator for the spring sits between the plates and its is operated, via a right-angle transmission, through a hole in the band of the case. The potence, much repaired in brass, is wedged to the bottom of the plate; it protrudes through a hole in the front plate. The counter potence, which is between the contrate and the staff, is riveted.
The long arbor for the dial slides into the pillar from the top and is there secured by a brass block; at the bottom it has a square which fits losely into the pinion of nine.
The astronomical gearing is housed within the vertical box behind the dial. It is an epicyclic construction, built into a frame which is solid with the large contrate wheel of 96. The frame revolves around an arbor riveted to the back of the dial; at the foot of this arbor is a fixed pinion of 10, which imparts motion to the first planet wheel. The frame carries the rete, and therefore revolves once in a syderial day. All parts of the epicyclic construction except the pinions are of brass.
The frame consists of a near-circular plate with four cylindrical pillars riveted to it, and a circular plate with contrate teeth, pinned to the pillars. The rim of the circular plate was brazed to the centre portion, but the teeth were cut after assembly. The "pillar plate" carries a curved piece of brass, pinned to two of the pillars, for poising the mechanism; in addition it has a bridge, pinned over two studs, in which the first and the second planet wheels are pivoted.
fixed ← 10 ┌ 16 5 6
── │ ── ── ──
40 ┤ 18 40 61 → sun
55 → moon
The pipes for sun, moon and rete are all friction-tight on their wheels.
The first and second planet wheels (40/16/8 and 18/5) are carried by a bridge, both ends of which are pinned over studs.
The revolving moon is achieved by 16 teeth cut into the solar disc meshing with a wheel of 16 mounted on the moon-hand. The solar disc and the entire moon-hand assembly are later (thought to be by Thomas Mudge, see Provenance).
Three conversions can be traced: the adaption of a conventional clock to become a monstrance clock; the reconstruction of the dial, and the conversion to balance spring.
The earliest conversion took place in 1560, when the clock acquired its present shape. The traces of touch-knobs in the upper ring of the bottom portion show that this part was originally meant to be a conventional horizontal timepiece with a 24-hour dial; indeed, the dishing of the visible surface of the ring suggests that it had already been marked with the hour numerals, which were subsequently scraped out and the ring re-engraved. This also explains the marked difference between the engraving of the band of the lower portion and the rest of the clock (particularly clear in the shape of the planetary symbols). The bottom portion would therefore appear to have been a complete clock (not a half-finished one) before it was converted to the present mirror-shape. As to its date: there is no clear indication for that, though it is likely that a fairly new clock was used for this purpose.
The later reconstructions of the clock are well documented. When Ferguson acquired it from Mudge in 1771 (see Provenance) he made a drawing of it; despite some discrepancies (notably in the scales that surround the astrolabe) this drawing is quite reliable, and it shows that at that time the astronomical dial already had its present solar disc, but there is no tidal dial and the revolving moon appears to be smaller. The primary reconstruction of the dial had therefore already taken place, and the superb workmanship of the new parts suggests that this was done by its first known owner, Thomas Mudge, some time prior to 1771. The high quality of the work suggests that Mudge also added the tidal indications, presumably at the instigation of Ferguson; this in turn necessitated extending the fixed central arbor of the dial (the length of the original arbor shows that there always was a revolving moon). It may be noted that although the general design of the reconstructed parts of the dial is correct, the design of the solar disc is unconventional in that the triangle, square and hexagon of the aspectarium are incomplete (thus alowing a clearer view of the astrolabe). The lines for the hexagonal aspect are marked with four-pointed stars (in stead of the usual six-pointed ones).
Mudge apparently left the movement as he found it, but the next owner, James Fergusson, was not so discreet. He describes it as having only "a light balance without a regulating spring", and proceeded to replace those parts, as well as the fusee. This conversion is not nearly as delicate as the earlier work, and was indeed probably Fergusson's own. It presumably took place shortly before 1776, the date of the description in his Common Place Book.
Since then the clock has not been interfered with any more.
Since the going train drives the rete of the astronomical dial all periods are expressed in syderial days.
Movement: great wheel - 3 revs. per syderial day.
escapement - 5062.5 beats per syderial hour.
duration - 3½ syderial days.
rete - 1 rev. per syderial day.
sun - 1 rev. in 24 hours; relative to rete one less rev.in 366 syd. days (i.e. year = 365 solar days; therefore 1 syd.day = .9973
mean solar days).
syderial moon - relative to rete 1 rev. in 27.5 syd.days. = 27.4249
mean solar days.
lunation - 29.7341 syd. days = 29,6529 mean solar days.
Clock: total height - 307 mm
diameter base - 162 mm
diameter vertical dial - 119 mm
Movement: distance between the plates - 34.5 mm.
HISTORY AND PROVENANCE.
There is an unsupported tradition that this clock once belonged to Robert Hooke (first mentioned by Smyth ), but the earliest source does not mention this, and the provenance must be considered doubtful.
The earliest undoubted source dates from 1776, when the astronomer James Ferguson (1710-1776) made a lengthy description and a detailed drawing of it in his Common Place Book. He noted that he had received the clock some five years previously as a gift from his fried, the watchmaker Thomas Mudge (Henderson, Milbanks). Since Mudge removed from London to Plymouth in 1771 the gift was probably on that occasion; how long Mudge had owned the clock is not known.
What happened to the clock after Ferguson's death is not clear. It was probably sold at auction in 1777, as happened to another old clock he owned 1). The next known owner is the watchmaker W.Finch in Hamstead, who is otherwise unknown. From him it passed, shortly before 1851, to Octavius Morgan (Smyth ).
Morgan showed the clock at the Antiquaries on 19th June 1851, and wrote a description for the Proceedings. From the facts that the language of the clock is french, and that one of the latitudes of the astrolab corresponds with Paris, he concluded that it was french, possibly by Oronce Fine. Morgan clearly refered to the side engraved for 48, even though it is clear from his description that he had seen the other, more telling, side of the disc. Octavius Morgan Bequest, reg. 1888,12-1,101.
Fergusson's Common Place Book was first investigated by Henderson (1867), but it was only Lloyd (1955) who recognized that the drawing represents the present clock.
No other clock or instrument, stamped with this maker's mark (which is unidentified) is known to exist. The mark presumably belongs to the early or lower portion of the clock.
The astrolabic dial and its back are based on two plates in: J.Focard, Paraphrase de l'astrolabe, 1st ed. Lyon 1546, 2nd ed. (revised by Jacques Bassentin) Lyon 1555. Cardinale (1986) recognised the design of the back in the second edition (from the ill. of the relevant page in A.J.Turner, Cat.Rockford, Astrolabes, p.5), but her conclusion that the clock was therefor also made in Lyon does not check with the latitudes of the astrolabe-discs (48' and 51'32). James Bassentin (Bassantin) was a Scot who worked in Lyon but returned to Scotland in 1562 (DNB). The copy of Focard 2 (1555) in the BL has an owner's inscription of the mathematical practicioner Humphrey Baker of London (Tailor (1954) 172-173).
Not only the back of the astrolabic dial comes from this source, the rete does, too. The pictures are:
J.Focard, Paraphrase de l'astrolabe (Lyon 1546): back (dated 1545) p.22; rete p.32. Lat. of London here given as 54' (p.157).
J.Focard, Paraphrase de l'Astrolabe ("Revue & corrigee par Iaques Bassentin Escossois, auec vne Amplification de l'Vsage de l'Astrolabe par luismesme aioutee") (Lyon 1555). Same blocks; back (dated 1545) p.19; rete p.28.
The back in Focard has the date the right way up; why the clock has it upside-down is unexplained.
Solar Cycle - Domonical Letter - Lunar Cycle (Golden Number).
The cycles of S.C and D.L. start at 1 = GF, which is correct for the Julian Calendar. The series begins with 27 = B. 1560 has S.C.1; the series therefore starts three years early.
The Lunar series starts at 1. The year 1560 has L.C.3: here, again, the series starts three years early.
The three series progress clockwise.
In Focard's diagram the series, which progress anti-clockwise, start at S.C.14 = D and L.C.7, which are correct for 1545.
The clock is not very practically constructed. It clearly started life as a (half-finished?) horizontal clock, with the movement and dial sliding into the case from the bottom, and an overlapping ring around the dial solid with the case (compare no. 1888,1-7,1). In the present clock the top portion can be unscewed from the bottom part, the column remaining solid with the top and the pinion at the bottom sliding off the arbor. The slightly later date of the top portion may also explain why the astronomical gearing is of brass while the rest of the wheelwork is of steel.
1) Paper preserved with the clock by Jacob Zech, 1525, in the collection of the Society of Antiquaries of London.
NB.: Feild (1554) gives latitude of London as 51' 34.
Cuningham (1559) has 51'30 (p.174).
Possibly the designer of the dial took the mean value of these two.
Notes about this clock among Morgan's notes (Arch.5).
When assembling care should be taken that the pinion at the bottom of the culumn is right-side up and rides easily on the square of the arbor. The column should be unscrewed when the movement is out of its case; otherwise the pinion will become loose in the case.
The male screw for the column is cut into the steel bridge. The female thread in the column is a brass spiral brazed inside the hole.
There are marked similarities between this movement and the much smaller CAI 2111.
Modern lay-out of the train!
All friction-tight connections under the dial now riveted solid.
There is a small circular indention in the centre of the ebony part of the revolving moon (trace of where it was mounted in the lathe?). Note that the revolving moon in Mudge's Lunar Clock is also constructed of ivory and ebony (or black-stained wood).
Spring very powerful! Certainly later: it appears to be ca.1800.
The raised bushes of the barrel caps are bent (not brazed) rings; they are original, as there are traces of gilding on them.
BIBLIOGRAPHY (Pauline Wholey – 2019)
Smyth (1851) W.H.Smyth, `Supplement to the Description of an Astrological Clock, belonging to the Society of Antiquaries', Archaeologia 34 (1851) 1 20.
Morgan (1852) O.Morgan, `Supplementary Observations on an Astronomical and Astrological Table Clock, together with an Account of the Astrollabe', Archaeologia 34 (1852) 293 298.
PSA - Proceedings of the Society of Antiquaries of London vol.1 - , London 1849 - (starting in 1843).
PSA 2 (1853) 176 (meeting of 19th June 1851).
Henderson 1 (1867) E.Henderson, Life of James Ferguson, F.R.S. (Edinburgh etc. 1867).
Henderson 2 (1870) E,Henderson, Life of James Ferguson, F.R.S. 2nd ed. (Edinburgh etc. 1870).
Postcards (1925) - British Museum, Set 77, Clocks from the 16th to the 18th Century ... 15 Pictorial Postcards (London? ca.1925). Envelope containing 6 pages of text and 15 postcards. There exist two issues; in the earlier one the postcards are slightly larger and they have no printed material on the back. NB: "No photographs seem to be available" (HJ [April 1923] 158).
Lloyd (1955) - H.A.Lloyd, `A clock recording planetary hours', JS 80 nos.9-10 (Sept./Oct. 1955) 389-394.
Lloyd (1958-1) H.A.L(loyd), `A.H.S. Visit to the British Museum', AH 2 no.6 (March 1958) 109 110.
Lloyd 3 (1964) H.A.Lloyd, Old Clocks, 3rd ed. (London 1964).
Lloyd (1964) H.A.Lloyd, The Collector's Dictionary of Clocks (London 1964).
Tardy 5 (1981, 1982) Tardy, The French Clocks, 5th ed., Part 1, 2 (Paris 1981) Part 3 (Paris 1982).
Tait (1983) H.Tait, Clocks and Watches (London 1983).
Cardinale (1986) 29-33 (noted Focard).
Aked (1986) - C.K.Aked, `Horloges de Table Astronomiques Françaises du XVIème Siècle' (Courrier des Lecteurs), ANCAHA 47 (Hiver 1986) 76-77.
Millburn (1988) J.R.Millburn, Wheelwright of the Heavens, the Life and Work of James Ferguson, FRS (London 1988).
Panicali (1988) R.Panicali, Orologiai del Rinascimento Italiano la scuola Urbinate (Urbino 1988).
Wenzel (1996) - J.Wenzel, `Das Astrolab an Uhren', AU 6/96 (December 1996/ January 1997) 36-46.
Text from 'Clocks', by David Thompson, London, 2004, p. 24.
Anonymous 'M' or 'W'.
Planispheric astrolabic clock
France, c. 1560
Height 30.7 cm, base diameter 16.2 cm, vertical dial diameter 11.9 cm
This rare French clock has a clockwork-driven astrolabic dial, with features similar to those on an actual astrolabe. The base houses a large spring-driven iron movement with fusee, verge escapement and balance but the brass balance-bridge and balance are not original. The gilt-brass base has fine engravings of the signs of the zodiac around the side, and its upper surface is engraved with concentric rings showing the Ptolemaic universe. The central column, engraved with the hours of the day and their ruling planets, conceals an arbor which drives the dial.
The planispheric astrolabe is marked for hours around the outside. Within this, a revolving rete with star pointers is engraved with a degree scale and the signs of the zodiac. To the left a steel circle carries a small bead to show the sun's position in the ecliptic. To the right a small moon revolves to show the moon's position in the zodiac and rotates to show its phase. The time is shown by a pointer fixed to the solar plate which revolves once per day. Under the revolving rete is a fixed reversible plate engraved with polar projections to show the positions of the stars. One side is for use at latitude 48° north, and the other side is engraved for latitude 51° 32' north, probably for London. The French inscriptions and the general design suggest that, although unsigned except for a gothic letter 'M' or 'W' on the base, the clock was made in France as a commission for a buyer in London, where in 1560 there were very few, if any, native clockmakers.
The rear dial is engraved with degree scales, a Julian calendar appropriate for 1560, and the signs of the zodiac. The upper central area has a circular table showing lunar and solar cycles of nineteen and twenty-eight years and a table of relevant Dominical letters. To each side scales show unequal hours. Below the centre a shadow square, for use in conjunction with the alidade, or sight, allows the instrument to be used to demonstrate angular measuring in surveying.
Octavius Morgan purchased the clock in 1850 from a London watchmaker. Before that, it had an illustrious history, being owned by the eighteenth-century astronomer and mathematician James Ferguson. He described it in his 'Commonplace Book' and executed a splendid drawing to accompany his description. He notes that his good friend Thomas Mudge gave him the clock and compares the wheel-work to his own:
'I confess that I was very glad to find I had hit upon the same sort of motions in a clock as had been done 215 years ago, but of which I knew nothing until I had seen it in this clock. And it is abundantly plain, that by comparing the wheelwork and numbers of teeth in this and in mine, I have not (and indeed could not have) taken the hint from this ancient German performance.'
Octavius Morgan Bequest.
- On display (G38/dc4)
- Acquisition date
- Britain, Europe and Prehistory
- Registration number