An English horary quadrant, 14th century. The copper-alloy plate engraved with six unequal hour lines, a shadow square with two scales each numbered 4 8 12, a quadrant arc 0-90 divided to 1 and numbered  30 45 60 75 . 2in. (51mm.) radius. Estimate: £50,000-80,000
The ‘Chetwode Quadrant’ was recently discovered by a metal detectorist, and is one of only seven of its kind known. This type of instrument was introduced into Europe from Islamic Spain as early as 1250 and analysis of the metal as well as the style of engraving confirms the date of this example as c. 1376. It is the oldest scientific instrument that Christie’s have ever sold.
DISCOVERY STORYHow a metal detecting enthusiast unearthed the Chetwode QuadrantRead more
The horary quadrant is marked with lines for unequal hours, to be used as a sundial to tell the time. Today we use equal hours, which divide the entire day into equal parts; unequal hours, however, divide the day by the amount of daylight. This means that in the summer an hour takes longer than in the winter.
An astrolabe rete. Attributed to Georg Hartmann, circa 1530. The unsigned rete cut for 27 stars, the design typical of Georg Hartmann, the ecliptic divided into houses of the Zodiac and numbered by 10° with serrations on the outer edge for each degree. 5 1/4 in. (13.5 cm.) diameter. Estimate: £10,000-15,000
Our next lot is the rete of an astrolabe, one of the most beautiful objects of celestial cartography from the period. Often described as an ‘astronomical calculator’ the astrolabe was a symbol of astronomy in the Renaissance. Among its over one hundred functions, it could be used to predict the location of the Sun, Moon, planets and stars, to tell the time and as a tool for navigation. The rete is at the heart of the astrolabe and would be rotated to simulate the movement of the stars in the sky.
SEVEN CENTURIES OF SCIENCEOnline sale, ends 29 OctoberBrowse sale
Because they were so complicated, astrolabes were as much collected as status symbols, to convey the owner’s grounding in astronomy, as they were actually used for performing astronomical calculations.
A reverse printed paper quadrant. Attributed to Walter Hayes (circa 1618-1696). Printed from a 5-inch Gunter-type horary quadrant by Hayes. 5 1/4 x 7 1/2 in. (13.4 x 18.9 cm.) Estimate: £1,200-3,000
At first sight the star map on this paper quadrant appears in mirror image, as does the lettering and numbering. This is because it was printed from a finely made brass quadrant. The actual inking and printing of a physical instrument is a very rare technique. Only seven such examples are known.
It is a peculiarly English phenomenon and just three makers are recorded as creating similar images — Elias Allen, his apprentice Walter Hayes (who made this piece) and Henry Sutton. Perhaps created as a virtuoso display of the maker’s ability to engrave a fine instrument, or to act as an archive of instruments previously made and sold to show to potential customers, the origin of these prints is still mysterious.
An English brass sector. George Adams, mid-18th century. The polished brass sector with 14 scales including rare scale for hours for sundial construction, signed G. Adams London. 6 in. (15 cm.). Estimate: £1,000-1,500
Instrument making in the 18th century underwent huge commercial change as demand for finely made instruments grew.
One of the best makers was George Adams (1709-1772), who received a royal appointment to George III. This brass sector would have been used with a pair of compasses to solve, amongst other problems, trigonometric calculations. A particularly interesting feature is a scale that could be used for the construction of sundials.
A Wheatstone wave machine. Probably made by John Newman, circa 1850. Signed on the top plate C Wheatstone Inv. 29 1/4 x 9 x 10 in. (74 x 22.5 x 24.5 cm.) Estimate: £20,000-20,000
The 19th century saw perhaps the greatest change in the history of calculating machines. New and inventive analogue mechanisms were still being constructed, such as the ingenious wave machine of Sir Charles Wheatstone (1802–1875). Digital mechanical calculators were also improved to such an extent that they became practical to use and economical to produce.
A Thomas de Colmar arithmometer. Paris, mid to Late 19th century. The 6 x 7 x 12 model signed to the brass plate THOMAS DE [Colmar], INVENTEUR, EXPOSITION 16 RUE DE LA TOUR DES DAMES / S’adresser, 44 RUE DE CHATEAUDIN, 44, PARIS No. 1846. 18 x 7 x 4in. (46 x 18 x 10.5cm.) in case. Estimate: £5,000-8,000
The famous Arithmometer of Thomas de Colmar (1785–1870) is one of the most successful products of this period of innovation, and it is testament to its ingenuity that is was produced globally and extensively copied well into the 20th century.
A rare K-model Enigma cipher machine. Heimsoeth & Rinke, circa 1936. Number K288, with complete electrical wiring, four aluminium rotors (one of which acts as a completely adjustable reflector) stamped I-III raisted ‘QWERTZ’ keyboard with crackle black painted metal case, in wooden carrying case with green night-time filter — with six additional rotors, thee aluminium stamped K296 I-III, K291, two Bakelite A17315 S III & IV. 13 x 11 x 6 in. (33 x 28 x 15 cm.) Estimate: £80,000-120,000
When Alan Turing cracked the Enigma cipher at Bletchley Park, it ushered in the modern age of computing. The cipher was fiendishly complicated and had quadrillions of permutations. Its baffling complexity is easily seen by examining the functioning of this Enigma machine.
An Apple-1 personal computer. Palo Alto, 1976. Estimate: £300,000-500,000
Our story culminates with the dawn of home computing and the 1976 Apple-1, produced by Wozniak and Jobs in the garage of his parents’ house. That revolutionary pre-assembled motherboard was the founding of what is now, not just the largest computing company in the world, but the largest company.
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