This instrument adopts the horizontal arrangement, as the Amici's microscope. Its most remarkable peculiarity, however, is that it is a catoptric instrument, that is a microscope whose objective is formed by a concave mirror. This new system for the microscopes was first used by Amici at the beginning of the last century, in order to reduce satisfactorily the chromatic aberration of the objective; in fact, all the microscopes built before the mid-19th century provided poor quality-images essentially due to the chromatic aberration of the object-lens. The instrument presented here has a very important historical value both for its peculiar features and for being one of the few existing microscopes ascribed to Jecker. With reference to the photoreproduction, the eyepiece is at the right end of the horizontal tube while the concave mirror is at the other end. The rays coming from the specimen go through the entrance hole and are first deviated by a plane mirror and then sent onto the concave mirror which gives an image of the specimen on the focal plane of the eyepiece. The tube of the microscope is held by two cylindrical bars screwed in a wooden case where the instrument accessories are kept. A knob controls the vertical movement of the stage then the focusing adjustment. Observations are possible only by transmitted light. The instrument is entirely of brass. Well-preserved. Overall height 30 cm. Signed: "Jecker ˆ Paris". Mid-19th century.
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