Incorporating a Full Traverse Table for Plane Sailing at Sea, c. 1700 Click on any image for a larger view.

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EARLY FOUR FOLD WANTAGE RULE WITH NAVIGATING / CALCULATING SCALES, English, c. 1700, signed "Peter Brock" within fleur-de-lys punches. The rule opens, with its three inset brass three-leaf hinges, to 36" (91 cm). There are external scales for inches (0 to 36 by tenths), for "Butt. Lying" (from 0 to 108, presumably for cask wantage), for "Beer Gallons" (0 to 125) and "Wine Gallons" (0 to 102). One "internal" side has a long nonlinear scale running 5 to 36, and a reversed nonlinear scale of 9 to 36, with short terminal arrays of (1, 2, 3, 4, 5, 6, 7), (_, 36, 16, 9, 5, 4, 2), (1, 2, 3, 4) and (12, 6, 4, 3). The final (internal) side has tables of (I, F) and (F, (I), presumably feet and inches, another of pounds, shillings and pence (from 1p 2s 4d to 6p 57s 0d), and a well designated double table for calculating the "Difference of Latitude" (i.e., the distance in miles between the parallels of latitude of any two places), and the "Departure" (the distance in miles between the meridians of two places, measured at constant latitude). Each measure is given here for every quarter point in four points of the 32-point sailing rose, i.e., for every 128th of a circle, or every 2.8125 degrees. Thus one has a full traverse table for plane sailing, as published in greater detail in most early books of navigation (see e.g., Robertson, The Elements of Navigation, 4th ed., 1780). Condition of this rule is worn, darkened, and a bit warped, although it is undamaged and the scales are essentially all quite readable. A significant rule, by this newly found maker. (7314) $3950.


The "Numerical Pocket Piece who teaches abroad, or privately at home," Click on any image for a larger view.

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THE "ARITHMETICAL MEDAL AND NUMERICAL POCKET PIECE," English, 1753, "Sold by I * Maddux, at the hand & pen in Brook Street, Holbourn." The cast bronze medal, 1-3/4" (45 mm) in diameter, carries on one face the "Numerical Pocket Piece who teaches abroad, or privately at home," with its "Table for Multipl'n. & Division by a new & short method," giving all integral products from 3 x 3 up to 9 x 9. The other face includes a table converting pence to shillings and pence, a table of multiples of twelve, and a "numeration table" giving place value of units, tens, ..., hundred millions. Condition is very fine, the medal retaining much of its gilding. A most unusual arithmetical teaching aide mémoire / pocket calculator. (7344) $1150.


By the Significant Early Rule Maker, dated 1704 Click on any image for a larger view.

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LARGE BRASS SECTOR BY ISAAC CARVER, English, 1704, signed "Is. Carver, fecit 1704." Opening to 18" (46 cm), the sector has a stabilizing strut which can increase the length to a full 24². The sector arms are divided 0" to 18" by tenths, and the strut is similarly divided from 18" to 24". The edge of the sector is divided to one-hundredth of an English foot. The sector arms are divided on both sides with a full complement of computational scales labeled "T, tan, S, Incli. M., Tan, Sine, Sec, Hours; C, sec, L, chords, C, Eq. P., Latitud, and Numbers," enabling, with a pair of dividers, all manner of trigonometric and logarithmic calculations, sundial construction, etc. Condition is good noting old repair to the sector hinge, with nearby losses to the engraving.

The maker was Isaac Carver, working c. 1668 - 1713 in Southwark, London, best known as an early maker of slide rules. Two boxwood slide rules are listed by Baxandall and Pugh, in the Science Museum collection, and one is recorded at the Museum of the History of Science in Oxford, that dated 1688. Carver was apparently one of, if not the first, maker of Everard¹s gauging slide rules (1683). And by 1741 the Imperial Academy had in its inventory an instrument by Carver, probably acquired in London by Peter the Great in 1698. The Websters list a sector in ivory, but we find no other example in brass by this significant maker. (8360) $4500.


Learning the new Metric System, c. 1805 Click on any image for a larger view.

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METRIC SYSTEM CONVERSION TABLETS OF FRANÇOIS GATTEY, French, c. 1805, entitled "Tablette pour convertir sans calcul les poids anciens en nouveaux, et réciproquement," and "Tablette ... les toises, pieds, pouces, et lignes, en mètres et parties de mètre, et réciproquement," respectively, and both signed in ink by Gattey himself. The two tablets are made of heavy card, 5" x 8-3/4" (12.5 x 22 cm) overall, bound in green edging and mounted on both sides with printed, hand-colored conversion panels. Each comes in its original card sleeve printed on both sides with instructions for use, and the two sleeves are stored in an outer card case. Condition is fine noting some browning and stains to the instructions, and losses to the little silk pull tabs.

Gattey (1753 - 1819) was charged, within the new agency of weights and measures, with unification of measures of mass. He went on to popularize the new metric measures, publishing several books and pamphlets, and these two unusual tablets, all in the early 19th century. Several examples of his works exist in the Bibliothèque Nationale. Rare. (7334) $1500.


Rare Multifunction Slide Rule for Chemistry Click on any image for a larger view.

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CHEMICAL ENGINEERING SLIDE RULE, Japanese, c. 1960, signed "Hemmi, Japan, No. 257." The 12-1/2" (32 cm) long rule is made of laminate over bamboo, metal bound, and fitted with double-sided sliding glass cursor. The two sides of rule and slider are divided with a total of 23 scales, including gauge marks for determination of atomic and molecular weights, temperature, conversion scales, pressure unit conversions, molar / weight / volume fractions, adiabatic compression and expansion, etc. In addition there are the standard scales of multiplication, roots, logarithms, exponents, etc. The outfit is in near new condition, complete with instruction manual and leather case. The Hemmi Slide Rule Company was established in 1895 (first as Henmi Jirou & Co.) They became a major manufacturer of both standard and specialized slide rules, introducing the model 257 in 1954. But within 10 years the introduction of electronic calculators initiated the precipitous decline in slide rule manufacture, and the Hemmi company eventually turned to electronics. (7316) $950.


A Most Rare Patented Calculator Click on any image for a larger view.

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THE "CALCULATEUR DIDELIN," French, c. last quarter 19th century, "Brevete France S.G.D.G. et Etranger." The 19-1/2" x 8-1/2" x 2-1/2" (50 x 22 x 6 cm) softwood case, with hinged lid and sides, contains a system of five lithographed tin rollers, plus a hinged overlay plate with a total of 150 (!) windows opened and closed by 30 independent shutter slides. The rotating tubes (for units, tens, hundreds, thousands, and ten-thousands) are printed with interest due for 30 different percentage rates (from 0.25% up to 9%). Condition is fine throughout noting a little wear and soiling. It is an intriguing and quite rare specialized calculator; we find no example in the published catalogues of the collection in the Science Museum in London, and but one in the Musee des Arts et Metiers, that one given to the Museum by Monsieur Didelin himself in 1892. (7337) $3500.


The Combining Power of Compounds Click on any image for a larger view.

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THE FIRST SLIDE RULE OF CHEMICAL EQUIVALENTS, English, c. 1815 - 1820, signed "Publish'd by W. Cary, 182 Strand, Jan. 1, 1814." The rule is made of thick printed paper applied to mahogany and varnished, measuring 2-1/2" x 12-5/8" x 3/16" (6 x 32 x 0.5 cm) overall. The slider scale is logarithmic, from 10 to 320. The body has two lists of chemical compounds (92 in all), each compound placed in the position of its quantitative combining power, based on oxygen at 10. The reverse has applied a very early owner's handwritten instructions by example, and the rule is complete with its early sewn chamois carrying sleeve with belt(?) loop (a remarkably early forerunner of the mid-20th century nerd's slide rule belt case). This is all contained in a modern protective mahogany box. Condition of the rule is good, noting water stains and slight edge wear to the paper.

This is a rare example of William Hyde Wollaston's 1814 slide rule, enabling straightforward calculations to find what weights of different elements or molecules combine to produce a given product weight (or conversely how much of each material results from decomposition). Wollaston presented his "Synoptic Scale of Chemical Equivalents" to the Royal Society in 1813, and William Cary (the important instrument maker) published his rule two months later. We have had two other early paper on wood chemical slide rules, one developed by Scholz in Vienna in 1821 (Tesseract Catalogue 68 Item 36), the other by Ehrmann in the 1820's (Catalogue 85, Item 36). But this is the first example of Wollaston's original we have been able to offer. More details on chemical slide rules are given by W. Williams (1992), who was able to locate only six other Wollaston ones surviving. (9385) $6500.


Patented French Calculator Click on any image for a larger view.

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THE "TACHYLEMME," French, c. 1880, signed "C.L. Chambon, Inventeur; Lith. Baster & Vieillemard, 97, B't. Port-Royal, Paris; Approuvé par la Societe d'encouragement pour l'industrie Nationale." This patented calculator has a fine 4" x 6-1/2" (10 x 16.5 cm) polished wood body with ebonized wood base, beveled glass top, and plated metal frame. The lithographed panel displays, through windows, the printed numbers on four cylindrical rollers for 1's, 10's, 100's, and 1000's. There are windows for percentage rates (of interest, etc.) of 1% to 6% by halves. External knobs allow setting any four digit number; one then sums the four displayed values for the result. Condition is fine noting a slight chip to the glass. Baster and Vieillemard are well known as fin-de-siècle Parisian lithographers of color postcards, publicity cards, etc. Chambon himself invented the "Tachylemme" in 1876. An uncommon device -- one is recorded as having entered the IBM collection. (9365) $1450.


Musical Scale on an Early Sector Click on any image for a larger view.

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A MUSICAL SECTOR, German or Italian, c. late 17th century, made of brass, reverse tapered in thickness, opening from 7-1/2" to 14-1/8" (19 to 36 cm). One side is finely divided with twin sector scales of equal parts (each scale divided twice 0(1)100; i.e., from 0 to 100 by ones), of "Lin Recta" 15(1)2, of "Lin 'square'" 0(1)60(5)90, and of a wonderful musical scale "fi, G, G-is, a, b, h, C, C-is, D, D-is, E, f." The other has twin sector scales of "Lin Cub" 1(1)50(5)120 and "Lin Circul" 60(5)45(1)6, noting a couple of tiny terminal fleur-de-lis marks . Condition is good with general surface wear.

This interesting sector has standard scales for computing distances, areas, etc. But it also has a musical scale of 12 notes, spaced nonlinearly and representing the differences in pitch. It is specifically German nomenclature, distinguished by the "-is" abbreviation sign (engraved here somewhat like the Greek beta) meaning "sharp", the "b" for B-flat, and the zigzag-h for B-natural (Jeffrey Dean, 2012; and see W. Apel, 1949, The Notation of Polyphonic Music, 900-1600). Such a musical scale can have many uses in the design and construction of instruments, for example calculation of lengths of lute strings or organ pipes, of string gauges or tensions, or even of bell diameters. The only other musical sector scales we have found are on very large German sectors (e.g. see R. de Pecker, 2007, and a particularly fine example at Oxford). (9395) $4500.


"Arithmetical Not Zoological" Click on any image for a larger view.

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FIRST FORM OF WEBB'S ADDER, American, c.1875, signed "C.H. Webb, N.Y., 'The Adder,' Patd. March 10th, 1868," #C671. Made of sheet brass on mahogany, 6-3/4" (17 cm) overall, this is the uncommonly found early form of Webb's "two-wheeled velocipede of figures." Described in detail by Kidwell in Rittenhouse (1, 12), it was succeeded by Webb's popular all-metal version. This is a good example of this American calculating instrument, in fine condition, with photocopies of Webb's instructions and glorious testimonials. The New York Times of 2 Jan. 1869 headlines "'The Adder' -- Arithmetical Not Zoological." And from Inventors and Manufacturers'Gazette of the same month, "This 'Adder' can easily be worked in a room where a dozen persons are engaged in conversation, and the operator himself can talk during the adding process without fear of blunders." Webb himself seems to have been a man of many talents. Under the pen name "John Paul" he was the "wise and witty New York correspondent" to the Springfield, Massachusetts Republican; he authored Wickedest Woman in New York, and was the playwright for numerous burlesque performances. (9303) $975.


One of the earliest dated French Sectors Click on any image for a larger view.

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ELEGANT EARLY SECTOR, French, 1681, signed by the maker, "pouilly a Paris, 1681," and for the early owner(?) "Boisdauid." Measuring 6-3/4" (17 cm) long (closed), it is constructed with two hinged brass arms gently tapered in thickness. The arms are engraved quite simply with only three doubled sector scales, as on the earliest French sectors: Les Cordes, Les parties Esgalles, and Les poligones (i.e., chords, equal parts, and polygons). Such a simple sector is illustrated in Henrion's L'Usage du compas de proportion, first published in 1618. Condition is very fine. Jean Pouilly, working c. 1650 to 1692, is certainly one of our favorite makers of scientific instruments of all time. He is responsible for the extraordinary hand held microscope (see Tesseract Catalogue 46 Item 8), for a graphometer decorated with human-headed floral worms (Catalogue 11 Item 45), and for the curious surveying instrument in the State Library of New South Wales. The present sector is important as an example of the early French design of this "calculating" instrument, and is one of the earliest dated French sectors. As to the owner, we do find the name appearing in late 17th century France, and our attention is drawn to a Captain Boisdavid leading 500 troops in Alsace: "Le 8 mars 1677, Boisdavid apparaît sous les murs du burg avec une troupe d'environ 400 hommes d'infanterie et une centaine de cavaliers ...." (from Chateaux forts d'Alsace). (9341) $4800.


Specialized "Napier" Rods from The Netherlands Click on any image for a larger view.

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SPECIALIZED CALCULATING RODS -- "NAPIER'S BONES" FOR SIZE AND WEIGHT CONVERSIONS, Dutch, c. 1800, with the partial trade label of "Dirk Van Den Bosch," mathematical instrument maker of Rotterdam. The fine mahogany case contains this complete set of 20 four-sided, 8-3/8" (21 cm) long, boxwood rods. Each rod is numbered on top with an integer from 0 to 9, and punched on each face with four sets of columns of nine numbers, each column headed by different lettered abbreviations. The latter are identified on a label in the case, being RV (Rheinland foot), AV (Amsterdam foot), HE (The Hague ell), HTP (Holland troy pound), AP (Amsterdam pound), NE (Netherlands ell), and NP (Netherlands pound). Further abbreviations have these letters preceded by V (for squares) or K (for cubes). In addition to the printed trade label and table of ratios (Verhoudingen) in the box, there is an old manuscript explanation written (in Dutch) by an early user. This note refers to van Swinden, the famous Dutch mathematician and physicist who wrote a major work on weights and measures, and was instrumental in bringing the metric system to the Netherlands. Condition is excellent noting some rods warped, and an old crack in the case lid.

This is the first such set we have encountered. In using it we find, for example, that one side of the "1" rod has columns for RV, NE, HE, and NE. The first column gives, to nine decimal places, the number of Rheinland feet in one Netherlands ell; the second column the reciprocal; the third the number of The Hague ells in one Netherlands ell; the fourth the reciprocal of that. The same face on the "2" rod has the same entries doubled, and so on to the "9" rod. Assembling a group of rods, and adding along the diagonals as with Napier's rods, we find directly how many of one unit are in any very large number of the other unit of length, or weight. With the "V" and "K" scales we can do this direct conversion for areas and for volumes, respectively.

The maker / retailer of this ingenious set is not found in the standard references. (9352) $9500.


Immediate Volumetric Computation Click on any image for a larger view.

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SHEPPARD'S PATENTED DOUBLE-SLIDE SLIDE RULE, English, c. 1880, signed for the maker "Stanley Great Turnstile Holborn London," for the inventor "Fred'k. A. Sheppard Patentee No. 160," and for the owner "Claude W. Atkinson." Constructed of fine boxwood, 13" (33 cm) overall, the rule has two two-sided slides running alongside each other. In the simple mode for volumetric calculations, the upper fixed scale "Length," the two sliding scales ("Breadth" and "Thickness"), and the lower fixed scale "Cubic Content" all have identical logarithmic divisions. To find the volume of a rectangular parcel, for example, one sets up the three dimensions and sees the answer immediately. To the reverse of the sliders are scales of square roots and linear scales of numbers. One edge of the rule has an applied (later?) paper scale of sines. We note a discussion of the relative merits of Sheppard's rule versus one of Dring and Fage, published in the 1883 English Mechanic and World of Science. An uncommon rule, in very fine condition throughout. (9342) $1150.


Calculator in Your Pocket, c. 1900 Click on any image for a larger view.

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THE CALCULIMETRE CHARPENTIER, French, c.1900, signed "Calculimetre, G. Charpentier, Brevete S.G.D.G." The 2-3/8" (6 cm) diameter calculator is made of nickel silver and brass, divided with logarithmic, square root, tangent and sine scales on both sides, the suspension affixed to twin cursors and a frontal circular scale. A milled edge allows one to rotate the main body against this suspension assembly. Condition is fine, the surface somewhat cleaned and scratched. The Charpentier calculator, a fine pocket slide rule, is analogous to the Mannheim design but with circular scales. It was covered by a French patent, and by a British one in 1882, and was listed in American Keuffel & Esser catalogues from 1895 up to 1927, and in Dietzgen catalogues (see Otnes, 1991). Despite this, surviving examples are relatively uncommon; here we are able to offer a good French one, complete with photocopies of instructions and of the original French patent papers. (9331) $1250.


By an 18th century Delft Instrument Maker Click on any image for a larger view.

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EARLY DUTCH MATHEMATICAL RULE, second half 18th century, signed "I. Reghter, Delft." This thick brass rule, 14-3/4" (37.5 cm) long, is divided on both sides with a total of six strongly nonlinear scales plus one scale of (Delft?) inches running from 0 to 12, the inches divided respectively into halves, thirds, fourths,..., twelfths (each inch 26.3 mm long). Scales are labeled cryptically "S,N" (1-32, 1-100), "V,R" (1-32, 1-125), and "L,T" (1-32, 1-125). Condition is fine except for several stains to the rule. We do find Reghter's trail in the references -- Zinner lists him as "I. Rechter a Delft," known for a planetarium (in the "Leiden Museum", #A182). King and Millburn describe this as a double-cone planetarium, and refer to Jan or Johannes Reghter (1730 - 1801) of Delft, "a highly skilled maker of compound microscopes, geometrical instruments, and electrical apparatus." Reghter was a published scientist in his own right. He designed and built an atmospheric electrometer which won a prize contest in 1786, and which led to a quarrel when van Breda, who had commissioned Reghter to develop this instrument, took all the credit and the prize (see Zuidervaart, 2006). We have had one other instrument by this maker, an unusual mechanical level with integral scale rule also with the undecoded "V,S,L" scales (Tesseract Catalogue 76, Item 34). (8309) $2950.


Complex Early Calculating Sector Click on any image for a larger view.

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MICHAEL SCHEFFELTS' MATHEMATICAL SECTOR, German, early 18th century, unsigned. This substantial brass sector is 7" (18 cm) long (closed), opening on a three-leaf hinge engraved both sides with a fine rose design. The faces bear a prolific number of single scales and doubled sector scales, for all manner of practical calculations in applied mathematics and engineering, including gunnery use, fortification design, surveying, navigation, plane and solid geometry, densities of materials, etc., etc. The numerals are punched in the brass, but the scale labels, the metallic symbols, and all the vignettes of polyhedral solids are boldly hand engraved. Condition is very fine noting light scratches to the surface.

The choice of scales, labels, and layout design on this sector is essentially identical to that illustrated in Michael Scheffelts' comprehensive book Instrumentum Proportionum..., published in Ulm, Germany, in 1708 (see illustration above). The few very minor differences show that the sector maker understood the mathematics, e.g., tangent scale running 0° to 45° (rather than 0° - 65° in Scheffelts), avoidance of engraver's error in the book (on the Cubic scale), etc. Michael Scheffelts was born in Ulm in 1652, and worked in several positions including teacher of mathematics. He was a very fine craftsman, and is known for several good instruments (see Zinner and Webster's Index). His book on the sector explains, in 148 pp and 12 full page plates, the construction and practical uses of his many scales. A rare example of Scheffelts' sector. (9311) $8500.


From the Thirty Year's War Click on any image for a larger view.

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SEVENTEENTH CENTURY GUNNERY GAUGE, German or Austrian, 1629, boldly engraved "Anno 1629." Rectangular in cross section, and tapered, the brass rule measures 13-1/2" (34 cm) long overall, including its cast and soldered double-sided bust handle. Each face of the rule is hand engraved, one with a scale of inches (labeled "Zol") from 0 to 12, each inch subdivided into the corresponding integral number of parts (e.g., the eleventh inch is divided into 11 equal parts!) Each inch measures approximately 24.1 mm, and is thus consistent with the local foot measure in a number of German city states (see Gilliland, SIS Bulletin 20, for an overview). The other three sides are divided nonlinearly, giving the weight of a cannonball of the measured bore diameter, for "Eisen Kugel" (Iron Balls) from 0 to 125 "Pfunt" (pounds), for lead balls (also over the range 0 to 125), and for stone balls (0 to 60 pounds). Condition is very fine.

Related gauges, one even with a bust, exist in the Dresden princely collections, illustrated in Grotzsch & Karpinski (1978, fig. 140). The present one dates from the Thirty Year's War (1618 -1648), which raged throughout Europe and devastated Germany. It is intriguing to seek an identification of the bust, assuming it is specific, but so far this is too speculative. What we do have is a wonderful dated survival from the early 17th century. (8377) $19,500.


Complex Scales by Engineer to Brunel Click on any image for a larger view.

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METFORD'S QUADRUPLE ENGINEERS SCALES IN IVORY, English, late 19th century, signed "Metfords Engineers Pocket Scales" and "Hudson & Kearns, London." The four ivory rules are each 6-1/2" (17 cm) long, of triangular cross section, and divided on all three sides with scales, constants, measured values, equations, etc. There are simple linear charting scales very finely divided (e.g., "6 inches to a mile"); relationships in triangles ("Hypoth= Base x Sec Angle at Base"); "Ordnance Scale;" expansion measurements for mercury, for glass tubes, for steel rods, etc; specific gravity of palladium, aluminum, etc; the logarithm of the force of gravity; the one-hundredth of a second of arc at the equator, measured in English feet; etc. We count 17 divided scales and numerous useful facts. Cryptic abbreviations on the ends of each rule form a table of contents. Condition is excellent except for a small chip at one end of one rule. The original leather bound case is present, lacking its end piece.

The inventor was presumably William Ellis Metford (1824 - 1899), a dedicated engineer who worked under Brunel for a time, and who is known for his improved surveying theodolite (see his high quality miniature theodolite "The Metford Theodolite with Repeating Circle," Tesseract Catalogue 64 Item 23.) One example of "Metford's Double Set of Ivory Pocket Scales suitable for Civil Engineers, Architects, and Land Surveyors" is presumably in the Science Museum -- we find it listed in the Catalogue of the Educational Division of the South Kensington Museum (1867). That set was signed by Pastorelli & Co.; ours by Hudson & Kearns, known especially as publishers in late Victorian England. A rare example of this complex set. (8357) $3950.


A Splendid Calculating Rule in Silver Click on any image for a larger view.

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EXQUISITE SILVER SECTOR, Continental, possibly Italian, c. early 18th century, bearing a punch mark, and with lovely shaped ends, and roses engraved to the hinge. Overall length is 4" (10 cm) closed, and the sector is beautifully engraved with doubled sector scales "Arithmetica, Geometrica, Cubica, Gradus Quadrantis." Additional scales give "demy Pied Roy," i.e., half the French linear measure of the King's Foot with subdivisions in inches and twelfths; 'Reinlendscher. 1/2 Fusz," i.e., half the Rhineland foot, likewise subdivided; and reminders of the sizes of one-pound cannon balls of iron, and of lead. The words are all beautifully hand engraved with flourishes, and the tiny numerals are all hand punched. Interestingly, the scales and their names are all read with the hinge to the right, rather than to the left as on typical French and English designs. Condition is very fine.

This is a diminutive example of an elegant form occasionally seen in brass; the design, execution, and terminal shaping may be compared with a Dutch sector by Metz (Tesseract Catalogue 46 Item 45) and with a c. 1700 Continental sector (Catalogue 71 Item 36). The only example we have seen in silver. (8267) $4800.


Complex Slide Rule for Cattle, Oxen, Sheep, Swine Click on any image for a larger view.

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EWART¹S ANIMAL GAUGE, English, c. 1840, signed ³The Cattle Gauge & Key to the Weighing Machine, arranged by John Ewart, Newcastle upon Tyne; J. Tree Maker, 22 Charlotte St., Blackfr¹s. Rd., London.² Measuring 9² (23 cm) overall, this double sided rule is made of brass-bound boxwood with ivory slider. The numerous tables and scales allow one to calculate the yield of meat from various types of cattle, oxen, sheep, and swine, depending on their live weight, length, girth, class of ox or bull, degree of fat, whether shorn, etc. This very finely made complex rule is in fine condition noting a bit warped with age. (7326) $950.


A Complex Circular Calculator Click on any image for a larger view.

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LORD'S CALCULATOR, English, c. 1900, signed "R. Waddington, Coventry." The 2-3/4" (7 cm) plated brass watch case is glazed in front, and fitted with two winding knobs and side mounting block. The calculator has four concentric circular scales (labeled A, B, C, and D), divided on silvered brass, the numerals colored in red and black. Two of these scales are independently rotatable by the knobs; no cursor is used. Condition is very fine and functional, noting a little wear to the finish. Lord's sturdy pocket calculator is quite rare -- even Hopp records only its existence, without details. (7299) $1350.


The Power of Radioactivity Click on any image for a larger view.

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RADIATION SLIDE RULE, French, mid-20th century, signed "SCRGR; CEA; GMP." The 13-3/4" (35 cm) long plastic rule is double faced, with double sided slider and cursor. It is divided with scales and nomographs for source activity, irradiation, intensity (over 10 powers of 10), photon energy, source distance, material (iron, concrete, aluminum, water, etc.) In fine condition, with the original leatherette case. (7349) $395. (ON HOLD)


Rare Swiss Mathematical Sector, c.1750 Click on any image for a larger view.

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EIGHTEENTH CENTURY SWISS SECTOR, c. 1750, signed "I.C. Bartenschlager, Schaffhavsen." This substantial mathematical sector is all brass, opening fully to 14" (36 cm). It is hand-divided and labeled (with all punched numerals and letters) on both sides with a full set of computational scales, including the doubled sector scales of sines, tangents, secants, cubes, chords, metals, polygons, arithmetic and geometric scales, plus edge scales of sines, tangents, logarithmic numbers, cannon ball diameters and cannon bore diameters. Condition is very fine, with traces of gilding. Bartenschlager is recorded in the Websters' Index for a ring dial, a table dial, a sector, and surveying instruments. Zinner records his dates (1713 -1799), and his production of mathematical instruments. Schaffhausen is first mentioned in 1045, and developed into a fine Renaissance city north of Zurich in northernmost Switzerland. We have here a rare example of an early Swiss instrument . (9332) $4500.




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