Achromatic microscope, by Shieck, no.32, Achromatic eyepiece, achromatic micrometer eyepiece (not fitting, but with instrument) triple o.g. no.5 (no case); o.gs no.8 (1 to 6 screwing together), in case (6), Amici prism on extending rod, stage forceps, live box, two small circular diaphragms added by T.H.C.

F. W. Schiek was a pioneer maker of achromatic microscopes in Germany, and this object resembles closely a model of Ploessl, of Vienna, who was also an early maker of achromatic microscopes. It dates from about 1840.

The round pillar is mounted on a flat folding tripod foot. At the top of the pillar the limb is attached at its middle by a short bracket which is mounted by a compass joint, thus allowing the limb to be inclined. The limb is triangular and the body is adjustable on it by rack and pinion, this serving as the coarse-focusing arrangement. Fine-focusing is effected by a fine-threaded vertical screw which acts on the stage.

The eyepiece is of the Huygenian form. There are three objectives with the instrument: one of these is numbered 4, another 5 and the third consists of six lenses screwing together numbered 1, 2, 3, 4, 5 and 6 respectively. Objective No. 4 consists of three achromatic doublets and has a focus of 0.18 in. Each of the lenses of the third objective is an achromatic doublet and the focal lengths in the order 1, 2, 3, 4, 5 and 6 are 1.6 in., 0.9 in., 0.6 in., 0.4 in., 0.4 in. respectively.