Beschreibung:

An extremely rare Dutch achromatic compound microscope, c.1805, unsigned , but attributed to Harmanus van Deijl of Amsterdam, with accessories in a mahogany box and a set of microscope preparations, c.1800, in ivory mounts with an accompnaying folded paper signed by the celebrated Amsterdam maker Abraham Ypelaar and another by his successor Daniël Scholte, in a two-drawer cabinet. The Microscope The stand is that of a typical compound microscope of the late 18th century. The flat folding tripod has a bevelled shoe into which slides the foot of the rectangular-section pillar. Into the central part of the pillar is cut a rack so that the stage may be moved by pinion. The pinion is turned by a knurled wheel that can be detached from the iron shaft. At the top of the pillar is a small drum with a slot to take a bar, which is held firm by a strip spring. The drum is so mounted that it allows the bar to move to the left or right for the so-called aquatic movement. The nosepiece of the optical tube screws into a ring at the end of the bar. The stage attaches by a bracket to the carriage of the rackwork focusing device. At the centre of the stage is a large circular opening to take the brass Bonanni spring stage, a plain glass disc, a brass or a wooden live box. On either side are wings, each with a hole for accessories. Unusually, the wing on the left is threaded, because the above-stage bull's-eye condensor is on a rod, which can move inside a sleeve that is screwed into position. The hole on the right-hand wing is plain, to accept the peg under the fish-plate, or the stage forceps. A lieberkuhn mirror can be screwed to the nosepiece of the optical tube once it is in position on the bar. Because the nosepiece is wooden and has shrunk slightly, the fit is now loose. Fitted to the front leg of the foot is a one-sided concave mirror, aperture 4cm. Over the mirror may be placed one of two light limiting discs, diameter 4.8cm., turned from lignum vitae. These reduce the reflected beam of light to apertures of 1.9cm. or 1.7cm. Hand tweezers are also provided. It is the optical tube that is the remarkable feature of this microscope. It is constructed from wooden tubes covered in embossed black leather (outer) and green vellum (inner). All the mounts and the nosepiece are made of lignum vitae, as are the two eyepieces and the two objective mounts that screw into place on the nosepiece. The eyepieces have screw-on dust protective caps, and the biconvex lenses are spaced at a distance of about 4cm. on the longer eyepiece (not numbered) and 3cm. on the shorter, which has attached to the side a small paper label with the umber 2 in ink. Both objectives are fitted with two lenses, as required to form an achromatic doublet. The lenses are close together, with a thin air gap. The more powerful objective has a small paper label bearing the number 6 ; the other no longer has a label. In use, the microscope gives a good image at a magnification of about 40x and 50x. The mahogany box is lined with green baize and contains most of the parts of the instrument in specific positions. At one side of the box is a drawer that contains the light limiting discs, the glass disc and the wooden live-box, as well as three long sliders, 13 x 1.7cm., of glass with spaces for 21 specimens in apertures cut into paper strips, each numbered. These specimens are listed, in Dutch, on pieces of paper. A modern tin box contains scraps of paper that hold specimens. The paper has writing in Dutch and the lid of the box is embossed "MARO" FABRIEKEN ROTTERDAM . There are a few other miscellaneous items that include two small ebony cups and two ebony discs for viewing white opaque objects, four brass washers, and some glass strips. Overall height closed -- 13½in. (34.5cm.) ; radius of foot -- 3.1/8in. (8cm.) ; length of optical tube closed -- 6¾in. (17cm.) ; diameter -- 1¼in. (3.2cm.) ; the case -- 9½ x 8 x 3¾in. (24.2 x 20.3 x 9.5cm.) The Cabinet of Microscope Preparatio