compound microscope by Bleuler – circa 1800
A impressive early compound microscope by John Bleuler – similar in design to the Jones Most Improved – it is signed on the base, “J. Bleuler, Ludgate Street, London”. An interior case label identifies the seller as J.C. Dennis, Optician. Interestingly, Bleuler was located at his Ludgate Street address from 1797-1822, whereas Dennis is placed at the address on his label (122 Bishopsgate St.) from 1850-1862. There is evidence of a removed horizontal label beneath the Dennis label. Since Bleuler’s label was similar is shape, it is most likely that this instrument was made by him sometime around 1800, and sold again by Dennis fifty years later. The microscope stands 17 ˝” tall in full upright position. It features a triangular shaped pillar upon which are mounted the elements of the microscope. The stage is attached with a rack and pinion gear. Focus is accomplished by moving the stage up and down. A small concentric knob controls tension of the focus knob. The plano-concave mirror is on a in semi-circular holder is attached to the pillar on a curved arm. The mirror itself is in excellent condition with only a few age veins passing through it. Between the mirror and stage is a condensing lens that can swing out in and out of the light path. The body tube contains four lens elements: two near the eyepiece, one in the center, and a fourth located at the joint above the nosepiece. In addition, there is a separate eyepiece to convert the instrument into a simple microscope. There are two lenses with lieberkuhns, and a third high power lens labeled “A” to complete the optical set. The main body tube has full aquatic movement adjustable with the knob on top of the pillar. Accessories include a stage condenser lens, lieberkuhn, fish plate, live box, a substage cone, glass stage disc, stage forceps (missing front pins), tweezers, talc box, separate accessory stage, two large sliders in mahogany mounts, and a shagreen covered case containing three ivory sliders and one brass slide. The microscope and its accessories are housed in an original mahogany case with lock (no key) and two front clasps. The case is in usable condition, noting two age cracks on the top, and a small (1/2” x 2”) piece missing from the top left rear. The microscope is finished in lacquered brass with complete coverage showing minor wear and age streaks commiserate with age. This is a fine, large scale example in the early development of the compound microscope.