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| A Pocket Refractometer |
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THE HERBERT SMITH CRYSTAL REFRACTOMETER, English, c.1910, signed "J.H. Steward Ltd., London, No. 549." Made of black enameled and clear lacquered squiggle-worked brass, 3-1/4" (8 cm) overall, the refractometer has a complex prism of high refractive index glass, internal calibration scale reading directly in refractive index of the sample, and right angle focusing eyepiece. Condition is fine complete with the original mahogany case, plus a list of mineral refractive indices. In use one places the flat surface of a natural or a polished crystal against the top surface of the instrument, illuminates through the window below preferably with monochromatic light, and reads the answer at the critical edge separating partially from totally internally reflected light. A fine miniature instrument for the identification of minerals, gem stones, etc. (8312) $1150. |
| A Miniature Digital Calculating Compendium | Click on any image for a larger view. Scroll to view more items. |
| ELABORATE SET OF NAPIER'S BONES IN IVORY -- A MINIATURE DIGITAL CALCULATING COMPENDIUM, English, late 17th century. The boxwood case, with original lift-off lid, measures 3-3/4" x 2-1/8" x 5/8" (9.4 x 5.4 x 1.7 cm) overall, and contains a "tabulat" board in boxwood and ivory (able to hold a 13-digit! number as multiplicand), 32 (of 39) 1-3/4" (44 mm) long ivory bones, and a wider ivory slip for calculating squares and cubes of numbers. Each "bone" gives the multiplication table for the integer on top multiplied by 1, 2, ...9. Diagonal lines show how to carry the second digits. All bones are original to the set, the same number punches being used on all bones and on the tabulat. There are exactly five different designs of these two-sided bones, bearing top integers of 0/9, 1/8, 2/7, 3/6, and 4/5. Multiple bones (at least five) are present for each of the five types, and thus for all ten integers, permitting multiplication of large numbers. A few (7) duplicate bones are lacking. Number punches suggest that the case was designed for 44 bones plus the square / cube slip, but in reality, the maker could only fit eight bones into each of the five slots, and today, after wood shrinkage, only seven per slot is comfortable. The set is in excellent condition throughout. John Napier (1550 - 1617) first described his calculating rods in 1617 in his Rabdologiae. The present variation of Napier's bones, the provision of a large number of two-sided slips (rather than a small number of four-sided rods) was advocated by Leybourn c. 1667 in his The Art of Numbring by Speaking-Rods: Vulgarly termed Nepeirs Bones (and in his Cursus Mathematicus). Leybourn's intention was to speed up the selection of bones in use (the four-sided ones being somewhat cumbersome). He proposed sets with 25 or 30 two-sided bones. Surviving examples are most rare -- we note one in the Whipple Museum of the History of Science (Bryden) and one in the Science Museum (Baxandall and Pugh), neither of which is in ivory. (7319) $13,500. |  |
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"A description of these rods according to their best and latest Contrivance: ...only whereas my Lord Nepair maketh them square, each Rod to contain four sides, these are made flat, consisting each Rod but of two sides.... one set of these Rods consisteth of five pieces, and therefore hath but ten Faces or sides.... For the orderly keeping and ready finding of these Rods, I have often (for my self and others) had a Box made of Walnut-tree or Pear-tree, with five partitions in it, each partition to hold five or six sets of these Rods, or more if more Rods were required...." (Leybourn, 1667) |
| Original Prize Medal for Photography | Click on any image for a larger view. Scroll to view more items. |
| PHOTOGRAPHIC PRIZE MEDAL, English, 1887, the 2-1/2" (6 cm) diameter bronze medal with a good brown patination, finely formed with a likeness of "H.R.H. The Prince Consort," patron of the "Photographic Society of Great Britain," and on the reverse with a wonderful image of the chariot of Apollo, for the Photographic Society of London. |  |
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The winner's name is engraved around the edge "W. J. Byrne & Co., Exhibition, 1887." The photographers Byrne & Co. are found in 1883 and 1900 directories at 1 Clarence Terrace, in the London Borough of Richmond upon Thames (home to Hampton Court Palace, Ham House, Kew Gardens, etc.) Condition is fine. (7389) SOLD |
| A Complex Circular Calculator | Click on any image for a larger view. Scroll to view more items. |
| 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. |  |
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| The Power of Radioactivity | Click on any image for a larger view. Scroll to view more items. |
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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. |
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| Elegant Variable Prism by Deleuil | Click on any image for a larger view. Scroll to view more items. |
| ADJUSTABLE FLUID PRISM DEMONSTRATOR, French, c. 1825, beautifully engraved "Deleuil, Rue Mazarine No. 21, A PARIS." Precision made of brass, 10" (25 cm) tall (minimum), this elegant demonstration apparatus features a liquid chamber with two hinged glass windows (their inclinations adjustable independently, reading against 0°-50° scales) and graceful stand with three leveling feet and extending pillar. In use one can direct light through the prism and observe dispersion as a function of prism angle and type (various isosceles, asymmetrical, perpendicular incidence, etc.), and of refractive index and absorption (by using different liquids). It is a fine optical demonstrator, in fine working condition, retaining some of its original bright lacquer finish. |  |
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This is a particularly early example of the work of Louis Joseph Deleuil, founder c. 1820 of the famous Parisian firm of instrument makers, located at #21 rue Mazarine only until c. 1826 (see Marcelin). (7409) $2950. |
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