Universal Microscope by Charles Chevalier, c. 1840
Microscope Achromatique Universal
Palace Royal, 163, Paris
Box 33 x 43,5 x 16 cm; high 36 cm.
This microscope, of the maison Chevalier, represents one of the best examples of art and engineering of the 19th Century in the field of microscopy. The vertical cylindrical pillar is screwed in a boss on the case and at the top ends with a compass joint, holding the squared section limb that is also pinned at the bottom of the pillar with a peg with a knurled brass handle. A short bracket is fixed to the limb and holds the horizontal body tube. On the rackwork cut on the limb run the pinions for the stage and for the large double mirror, with a plain side of 50 mm and concave side of 83 mm diameter. The mirror can be oriented by a gymbal and two knurled knobs. The coarse focus screw is on the right side of the limb; the fine focus is by a vertical high precision screw, both the screws move the gearset of the stage.
The stage dovetails into the bracket, has mechanical movements on the horizontal plane and on the top has a blackened glass surface, with fitting for two brass clips (one is missing). Below it, a condenser with lens and a disc with four rotating holes in a bayonet fitting provides the desired illumination. An alternative plane stage in blackened brass is present: on it can be mounted a brass circular disc with two fixed clips for small size slides and on its top there is a circular housing for a Buonanni-type spring. The horizontal body tube has rack and pinion adjustment to the graduated eyepiece extension tube, engraved with a scale 0-80 mm. The objective is mounted on a right-angle component containing a prism and is attached via a bayonet fitting to the body tube. The mounting permits the body tube to be swivelled through to 90° on top of the short brass bracket; we suppose it had other accessories for different observations (see "Des Microscopes et de leur usage", C. Chevalier, 1839, first edition, plate 4). The instrument can be set in the vertical position; an objective collar is used in this configuration.
All the parts of the microscope and all of the accessories are engraved. The assembly number assigned to the instrument is 4. The large mahogany case has a lock, key and a brass handle; it contains a drawer where are housed two trays, both lined with green velvet and arranged one on the top of the other, and a lower level.
The first tray houses three Huygenian eyepieces with bayonet fitting, the substage lens condenser with a disc with four apertures, an objective collar for objectives fitting when the microscope is set in vertical position, an Amici-type camera lucida; the last place is empty but could accomodate a positive lens in a rectangular frame to attach to the camera lucida to correct the operator's eyesight (missing).
In the second drawer there are two brass button lenses objectives with a bayonet fitting; the first one is engraved on the rim with two rough lines and its two buttons are engraved respectively "2" and "3"; the second objective is engraved with three rough lines on the rim and its three buttons are engraved "+", "++", "+++", respectively; a further objective is fitted with a lieberkuhn. Finally, a stage micrometer in a brass mount engraved Millimetre en 100 Parties, signed Charles Chevalier Palais Royal, and a rectangular glass cell. The forceps and the bull's eye are missing. The green velvet tray can be lift out and under it there is still room for other accessories, with a large wooden slide present. We note the letter "beta" printed on one side of both trays.
The microscope is stored in the bottom of the drawer, with other accessories, on supports lined with green baize; a Nicol prism polarizer and a two-parts optical tube with one lens in each part are included. In a wood section are a translator plate and a galvanic device by Ploessel both made of brass and signed Charles:Chevalier. The first item is to gently move the position of the sample during an observation, the second one is made with two ferrules that can be connected to an external electricity source (e.g. a Daniel cell) to permit the observation of its effects on the sample (see this picture for example).