The Harvard Model Microscope with inclination and rack and pinion
The microscope is signed on stage: Bausch & Lomb Optical Co. and is marked on the limb with the 1876 and 1885 patent dates. The serial number, which us usually stamped on the case, is absent. Dating is approximate. This is an example of the Bausch & Lomb "Harvard" model microscope.
The body of the microscope is constructed in bright lacquered brass, while the base has a bronzed brass finish. The height of the tube can be extended by means of a drawtube. The drawtube has a Society Screw on the lower end to accommodate very low power objectives and other accessories. The microscope can incline. The coarse focusing is by rack and pinion and the fine focus utilizes a micrometer screw, which operates the patented B&L mechanism. The substage consists of a Wale type iris diaphragm, It is stamped with the Wale patent date, June 6, 1876. The mirror is adjustable on its swinging arm and is double sided with plane and concave glasses; it can be positioned above the stage to illuminate opaque objects. The microscope is supplied with two B&L eyepieces, two B&L objectives (marked 1/4 and 3/4) with their brass canisters.
This model was supplied in several versions. This particular example is the most elaborate version having the ability to incline and having rack and pinion coarse focusing. The most simple version lacks inclination and rack and pinion focusing while the intermediate version can incline, but retains push-tube coarse focusing.
The following catalog description states that since the Faculty of the Harvard Medical School made suggestions for the design of this model, it was given the title the “Harvard Microscope”.
"The leading idea in the construction of this instrument was to get the nearest approach to the simple pattern, used so extensively in Europe, and combining with it those modern improvements, without which any microscope may be considered incomplete. Members of the Faculty of the Harvard Medical School have been interested in its construction and have made a number of valuable suggestions, which have been embodied in it. In recognition of the favor thus shown, we have given it its name. Considering the work, the various adjustments and price, it will be found to bear favorably a comparison with foreign instruments of similar construction. The stand is made entirely of brass and so proportioned that it will give the most effectiveness to the various parts. Although constructed so as to allow its convenient use in an upright position on an ordinary table, it still gives sufficient range of adjustment for all ordinary work. The base is of the horse-shoe form with a projection at the back to give it steadiness when the body is inclined. Coarse adjustment is by a sliding tube in a sleeve, provided with a spring which reduces the friction and retains a smooth movement; fine adjustment is by micrometer screw with milled head of more than ordinary size, acting on our patent movement. The main tube as a draw-tube with a mark indicating standard length. The stage is large and stiff and provided with spring clips; our iris diaphragm is attached to its lower surface in such a manner as to allow its centering and entire removal for oblique light. The mirrors are plane and concave and swing with the mirror-bar to any obliquity below the stage and above it for the illumination for opaque objects. No.515A is with solid pillar and arm while B is arranged with joint for inclination of the body."