A rare and important French Compound microscope to the design of the duc de Chaulnes, unsigned, the split pillar, one bar fixed, the other sliding against it, carries the brackets holding the optical body tube, course focusing by rack-and-pinion to the back moveable bar, clamped in position by locking screw to the fixed part of the pillar, fine focusing control by long iron screw, the body tube containing three convex double lenses held in two supporting collars attached to the moveable part of the pillar, the foot of the pillar attached to a rectangular brass and ebonised fruitwood frame with four levelling screws at the corners, curved supports hold the rectangular stage platform, a central aperture allows light to enter the body tube by reflection from a plano-concave mirror fitted to the base framework (mirror missing), a particular duc de Chaulnes feature is the micrometer speciman holder, on one end of the stage are grooves to attach the base of the micrometer by locking screws, the specimen is held by a vice at the end of a moveable arm, which can be moved in an arc by a pinion, the arm may also be advanced along the axis of the stage by a micrometer screw, this has a large count-wheel with 100 divisions on its rim, and a pointer with a vernier comprising 10 dots spread over nine-tenths of a unit division, one complete turn through 100 units advances the specimen just 1mm, the well-constructed body tube (length 9 1/8in., diameter 2 1/8in.) screws together at the positions of the eye lens, field lens, and objective cell, on top is a screw-on dust cap, and below an internal thread takes the objectives, of which five are present, the lenses are in clear glass, and appear to be of good quality, the large field lens has a diameter of 49mm, and a thickness of 9mm, with walnut cabinet 17¾ x 12¾ x 7/8in. (450 x 322 x 200mm) the drawers on three sides hold accessories or specimens, one drawer has eight fitted sockets for objectives, the top has filets to locate a cover probably formerly glazed, also associated is a tray on four feet made of stained softwood with bun feet, the top covered in marbled paper (this was probably to preserve a table top from scratches made by the levelling screws in the microscope base), ten preparations are in the form of strips of thick glass sandwiching the substance, the strips held together by paper stuck to each end, on some the same marbled paper as on the surface of the display tray is used, the slides measure 100 x 18mm, or 64 x 21mm (approx), each is labelled in French by pen, in a 19th Century hand, the substances being as follows: Sel de cuisine, Sel de Tartre, Sel de Tamarix, Sel ammoniac, Salpetre de la poudrerie, alum, couerose, nitre, Salpetre, sel gemme, Sel D'oxalique [?], other specimens are 8 squares of cloth on glass, two wooden sliders for a lucernal microscope, two glass rectangles and one of ebony, sundry accessories include wooden eye-cup, stage forceps and stage pin, tweezers, screwdriver with ebony handle and a small free-standing specimen holder with a circular base and a collar to hold a watch-glass or similar support - base 11 x 7 1/8in. (280 x 180mm); overall height 16½in. (42cm.)See Colour Plate and detail

A rare and important French Compound microscope to the design of the duc de Chaulnes, unsigned, the split pillar, one bar fixed, the other sliding against it, carries the brackets holding the optical body tube, course focusing by rack-and-pinion to the back moveable bar, clamped in position by locking screw to the fixed part of the pillar, fine focusing control by long iron screw, the body tube containing three convex double lenses held in two supporting collars attached to the moveable part of the pillar, the foot of the pillar attached to a rectangular brass and ebonised fruitwood frame with four levelling screws at the corners, curved supports hold the rectangular stage platform, a central aperture allows light to enter the body tube by reflection from a plano-concave mirror fitted to the base framework (mirror missing), a particular duc de Chaulnes feature is the micrometer speciman holder, on one end of the stage are grooves to attach the base of the micrometer by locking screws, the specimen is held by a vice at the end of a moveable arm, which can be moved in an arc by a pinion, the arm may also be advanced along the axis of the stage by a micrometer screw, this has a large count-wheel with 100 divisions on its rim, and a pointer with a vernier comprising 10 dots spread over nine-tenths of a unit division, one complete turn through 100 units advances the specimen just 1mm, the well-constructed body tube (length 9 1/8in., diameter 2 1/8in.) screws together at the positions of the eye lens, field lens, and objective cell, on top is a screw-on dust cap, and below an internal thread takes the objectives, of which five are present, the lenses are in clear glass, and appear to be of good quality, the large field lens has a diameter of 49mm, and a thickness of 9mm, with walnut cabinet 17¾ x 12¾ x 7/8in. (450 x 322 x 200mm) the drawers on three sides hold accessories or specimens, one drawer has eight fitted sockets for objectives, the top has filets to locate a cover probably formerly glazed, also associated is a tray on four feet made of stained softwood with bun feet, the top covered in marbled paper (this was probably to preserve a table top from scratches made by the levelling screws in the microscope base), ten preparations are in the form of strips of thick glass sandwiching the substance, the strips held together by paper stuck to each end, on some the same marbled paper as on the surface of the display tray is used, the slides measure 100 x 18mm, or 64 x 21mm (approx), each is labelled in French by pen, in a 19th Century hand, the substances being as follows: Sel de cuisine, Sel de Tartre, Sel de Tamarix, Sel ammoniac, Salpetre de la poudrerie, alum, couerose, nitre, Salpetre, sel gemme, Sel D'oxalique [?], other specimens are 8 squares of cloth on glass, two wooden sliders for a lucernal microscope, two glass rectangles and one of ebony, sundry accessories include wooden eye-cup, stage forceps and stage pin, tweezers, screwdriver with ebony handle and a small free-standing specimen holder with a circular base and a collar to hold a watch-glass or similar support - base 11 x 7 1/8in. (280 x 180mm); overall height 16½in. (42cm.) See Colour Plate and detail

Details

A rare and important French Compound microscope to the design of the duc de Chaulnes, unsigned, the split pillar, one bar fixed, the other sliding against it, carries the brackets holding the optical body tube, course focusing by rack-and-pinion to the back moveable bar, clamped in position by locking screw to the fixed part of the pillar, fine focusing control by long iron screw, the body tube containing three convex double lenses held in two supporting collars attached to the moveable part of the pillar, the foot of the pillar attached to a rectangular brass and ebonised fruitwood frame with four levelling screws at the corners, curved supports hold the rectangular stage platform, a central aperture allows light to enter the body tube by reflection from a plano-concave mirror fitted to the base framework (mirror missing), a particular duc de Chaulnes feature is the micrometer speciman holder, on one end of the stage are grooves to attach the base of the micrometer by locking screws, the specimen is held by a vice at the end of a moveable arm, which can be moved in an arc by a pinion, the arm may also be advanced along the axis of the stage by a micrometer screw, this has a large count-wheel with 100 divisions on its rim, and a pointer with a vernier comprising 10 dots spread over nine-tenths of a unit division, one complete turn through 100 units advances the specimen just 1mm, the well-constructed body tube (length 9 1/8in., diameter 2 1/8in.) screws together at the positions of the eye lens, field lens, and objective cell, on top is a screw-on dust cap, and below an internal thread takes the objectives, of which five are present, the lenses are in clear glass, and appear to be of good quality, the large field lens has a diameter of 49mm, and a thickness of 9mm, with walnut cabinet 17¾ x 12¾ x 7/8in. (450 x 322 x 200mm) the drawers on three sides hold accessories or specimens, one drawer has eight fitted sockets for objectives, the top has filets to locate a cover probably formerly glazed, also associated is a tray on four feet made of stained softwood with bun feet, the top covered in marbled paper (this was probably to preserve a table top from scratches made by the levelling screws in the microscope base), ten preparations are in the form of strips of thick glass sandwiching the substance, the strips held together by paper stuck to each end, on some the same marbled paper as on the surface of the display tray is used, the slides measure 100 x 18mm, or 64 x 21mm (approx), each is labelled in French by pen, in a 19th Century hand, the substances being as follows: Sel de cuisine, Sel de Tartre, Sel de Tamarix, Sel ammoniac, Salpetre de la poudrerie, alum, couerose, nitre, Salpetre, sel gemme, Sel D'oxalique [?], other specimens are 8 squares of cloth on glass, two wooden sliders for a lucernal microscope, two glass rectangles and one of ebony, sundry accessories include wooden eye-cup, stage forceps and stage pin, tweezers, screwdriver with ebony handle and a small free-standing specimen holder with a circular base and a collar to hold a watch-glass or similar support - base 11 x 7 1/8in. (280 x 180mm); overall height 16½in. (42cm.)
See Colour Plate and detail

Lot Essay

The instrument follows the pattern of that devised by the French aristocrat, Michel-Ferdinand d'Albert d'Ailly, duc de Chaulnes (1714-1769), a physician, soldier, and at various times President of the Academie des Sciences, Paris. The model was published in his Description d'un microscope et de differents micrometres (Paris 1768). The construction is similar to that employed by the celebrated London microscope maker John Cuff (c.1708-1772), who produced in 1743 a new model to the design of Henry Baker FRS. The duc de Chaulnes is known particularly for introducing precision measurement to microscopy, and his published design had a stage micrometer and a micrometer in the body tube just below the eyepiece. Some microscopes were made with two micrometers in very costly and elaborate rococo stands. One was for Louis XV, another for the King of Poland, while that thought to have belonged to Madame la Marquise de Pompadour is now in the J. Paul Getty Museum. There are only seven of this type known in the world, made between 1750 and 1755; they are listed in Jean-Neree Ronfort 'Science and Luxury: Two Acquisitions by the J. Paul Getty Museum' The J. Paul Getty Museum Journal 17(1989), 66-81(p.73). In contrast with these salon pieces, there is only the one extant microscope, preserved in the Istituto e Museo di Storia della Scienza at Florence, that follows the plan shown in the illustration to the 1768 book of the duc de Chaulnes. The illustration, the Florence instrument and the present microscope all have a vernier pointer on the micrometer wheels. The rococo versions have single, clock-type pointers. The present microscope bears a closer resemblance to the duc de Chaulnes' illustration than the instrument in Florence. The pillar, levelling screws, and body tube correspond, but there is no eyepiece micrometer. It is probable that the date of manufacture is after 1765, but it could be later. It is known that Claude Simeon Passemant (1702-1769) was involved with the duc de Chaulnes, having made some lenses for him in about 1750. Passemant also made copies of Cuff-type microscopes, and he was a first-class craftsman. Although there are pointers to suggest a date near 1770, there seems no possibility of attributing this microscope to Passemant's workshop with any certainty. The use of micrometers fairly soon died out, because the optical image was not sufficiently good for fine measurements. The micrometer in microscopy did not develop until after 1830. The specimen slides and tray are possibly 19th Century

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