Trécourt & Oberhäuser, early drum microscope, ~1837
This is a very early European drum-type microscope, most likely made by Trécourt & Oberhäuser before 1840. The microscope is made of lacquered brass with no blackened parts. The coarse focusing adjustment is obtained by sliding the optical tube, the fine by a knurled screw, which raises the stage top. Illumination is carried out via a rotatable flat mirror. The optical equipment of the microscope consists of two eyepieces and one objective with three stacking button achromats. In this case there are no recesses for further optics except the second ocular, so it is to be assumed that this instrument is kept except for the incident light in the original equipment.
The optics of this microscope consist of two eyepieces and an objective. The base of the round foot is covered with chamois leather, similar to the case inner lining, on which a sticker (assumed to be old) has been glued, with the inscription: FRAUENHOFFERS MICROSCOPE. For storage of the microscope, the base is unscrewed and the instrument is stored in a mahogany case padded with brick-orange colored chamois. The case there is only one recess for an additional ocular.
This microscope is an embodiment of the drum-type widely used by Georg Oberhäuser and other mid to later 19th century European makers, mostly from France and the German lands. While in the late 1830s Oberhäuser already offered his instruments with dark and matte stage surfaces, thus avoiding disturbing reflections during observation of slides, Simon Plössl and Friedrich Wilhelm Schiek still delivered their instruments with clear lacquered table surfaces until 1840. The stage surface of the instrument shown here is also lacquered bare brass, which suggests a dating before 1837 (modified after Mappes).
The mis-spelled reference to Joseph von Fraunhofer (1787–1826) is merely generic. Although this brilliant Bavarian inventor and scientist is known to adopt the drum microscope, originally invented and developed during the 18th century by Benjamin Martin (see the relevant items from my collection here and here), very few of his original microscopes have survived. This undoubtedly results from his early death at the age of 39. However, the idea was taken by several other microscope makers, most notably by Johann Georg Oberhäuser (1798 -1868), to become one of the most commonly used designs in Europe till the end of the 19th century.
Oberhäuser attended high school in his hometown Ansbach (Middle Franconia), with the intent of becoming an engineer. Due to the premature death of his father in 1812, he became an apprentice mechanic at the University in Würzburg in order to support himself. In 1816 he moved to Paris, and came in contact with the opticians Trécourt and Bouquet. In 1830 they started a three-way partnership at 19 Place Dauphine, yet in 1835 Bouquet departed, leaving Oberhäuser and Trécourt to do business together. They introduced their drum microscope in 1837 and very quickly they earned a good reputation for producing affordable and solid instruments with excellent achromatic lenses. In 1854, Oberhaeuser invited Edmund Hartnack (1826 – 1891), who married his niece, to work as an apprentice in his his workshop. By 1857, Hartnack had become a full partner in the business.
The attribution of this unsigned microscope to Trécourt and Oberhäuser is rather straightforward, based on existing parallels of the case with its elaborated inner lining, the unblackened stage and the overall workmanship. All these attributes may suggest the earliest dates of production by the company. It appears that in the early days, Georges Oberhäuser was supplying unsigned instruments to retailers.
I would like to acknowledge the fruitful discussions that I had about this interesting microscope with Drs. Joseph D. Zeligs, Jeroen Meeusen and Timo Mappes, who supplied me with some of the historical information contained here.
References: References to the later small "microscope d'hospice" by Oberhäuser and his various partners are vast (for example, Mappes and the references therein). However, there are very few examples, known to us, of this early form of the model. A good example, perhaps the earliest of this kind, is in the Balasse collection, signed: Bouquet et Georges Oberhaeuser à Paris. It should date to around 1830, when the partnership just began. Accordingly, it bears very early features especially in the accessories. Another example is in the same collection, closer to ours and also unsigned but missing the case. Below are the two closest parallels with their cases, both signed.
Private collection. Out of six drum microscopes signed by Trécourt & Oberhäuser in this collection, this is the only one that comes with this type of case.
Microscope offered for sale on eBay, 15/9/01: "Cased Chevallier Drum stand with two oculars and two button objectives. The stand is 10 1/2" high (closed) and is signed on the barrel, L'Ing Chevallier/Opticien du Roi/Vis a Vis le Marché aux Fleurs/a Paris. The mirror has a single plano surface and is in good condition. Coarse focus is by movement of the tube,while fine focus is achieved by adjustment to the stage. The circular base unscrews when the microscope is stored in its case."