Ernst Gundlach - Patd Jan. 21, 1879

The College Microscope

(Previously called the “Physician’s Microscope No. 1”)

Gundlach College microscope Gundlach College microscope
Gundlach College microscope Gundlach College microscope
Gundlach College microscope Gundlach College microscope
Gundlach College microscope accessories

With the draw-tube partially extended, the microscope measures about 14-inches in height as shown in the photos. The stage is glass, held in a nickel-plated brass frame, on which is Gundlach's patented mechanical slide carrier.

Among the accessories are three Gundlach objectives with canisters, a 2-inch, a 1/5, and a divisible lens marked 2/3 and 1 1/2, two eyepieces, and a substage aperture fitting. The case with lock and key has two internal drawers. Within the case is an instruction card by L. R. Sexton located at 29 Stone St. Rochester NY. Lewis R. Sexton was the sales agent for Gundlach microscopes during the years 1879-1884.

Gundlach College microscope Gundlach College microscope

The following was extracted from The Journal of the Royal Microscopical Society, 1882, pg. 670

Gundlach College microscope

Gundlach’s College Microscope—This Microscope, till now called the “Physician’s Microscope No. 1” is shown in Fig. 117. Its speciality consists in the adjustments, of which there are four, thus described (from the maker’s catalogue) :

( 1 ) A rack-and-pinion movement; (2) a sliding adjustment of the body; (3) a micrometer-screw, and (4) a combination of micrometer-screws giving a slower motion than has ever been brought into use before. The racks and pinions are cut with some new and original tools and with the greatest exactness."

Gundlach was the first to think of the advantages of the combination of the sliding adjustment with the rack and pinion, and to bring out a series of Microscopes on this plan. The former allows the body to be removed for changing objectives; and, by combining the two, the body may be made to stand so high that first-class low-power objectives may be used on these stands. Lower powers may be used on them than most large stands will allow.

The ordinary fine adjustment is by micrometer-screw acting on Gundlach’s new frictionless roller motion, patented in 1879. This motion is free from the fault of displacement of the optical axis, from so-called loss of motion, and from lateral motion, while it has twice the old extent of motion.

In working high powers, microscopists have felt the need in some work of a slower motion than that of the ordinary micrometer-screw, which cannot be made much finer and still be durable enough. This need is now supplied by the combination of two screws which give a resultant motion equal to the difference in the threads employed. One of these screws is a little coarser than the ordinary micrometer-screw, and may be used alone as a fine adjustment, and a change can be made instantly from this to the finer motion. Either motion is given by one milled head next to the top of the pillar, and the change is made by turning a smaller clamping screw having its head over the fine adjustment screw. By tightening the clamping screw, the adjustment is in order for the work of the combination; by loosening, for that of the coarser screw only. As the thread of this is a very little coarser than the ordinary micrometer- screw, it alone gives a better motion for medium powers than the fine adjustment in common use, a second advantage of the invention. the combination of screws in use on these Microscopes gives a motion equivalent to that of a screw having three hundred and sixty threads to the inch. Any desired combination can be made.

The stage consists of a strong, polished glass plate, made secure by a brass frame, which is nickel-plated. The glass plate has a hole in the centre, and is ground to permit the greatest obliquity of light. A new object carrier, consisting of an ornamented brass frame, with a rest for the object slide, removable clips, and two handles, moves with evenness upon the stage, to which it is pressed by lever springs, with double joint, to permit motion in every direction, and from which it is kept by frictionless pins that do not scratch the stage. The whole carrier can be removed and its place supplied with spring clips.

The sabotage slides along the mirror-bar, thus keeping the diaphragm or other accessory concentrically with the mirror upon the object with central as well as oblique illumination. It can be removed without interfering with the mirror.

The diaphragm is of novel construction, and is fitted to the substage. It is of such form that it can be brought close to the slide, and its openings brought in use without changing its position on the mirror-bar.

The mirror-bar swings to an anglo of 45° above the plane of the object, allowing the mirror to be used as a condenser on opaque objects. The mirrors have their centre of motion around the point where the optical axis intersects the plane of the object.

The Jan. 21, 1879 patent covers Gundlach's frictionless fine adjustment, the substage, and the stage slide carrier.

Gundlach College microscope-fine_adjustment.jpg

Gundlach College microscope differental screw

As mentioned elsewhere on this site, there was a collaboration on the production of microscopes between Ernst Gundlach and the firm Yawman & Erbe. With the College Microscope, Gundlach incorporated a differential screw mechanism onto the fine adjustment, which was patented by Philip Yawman on Aug. 15, 1882. The following description of the operation of this differential screw was extracted from the Odontographic Journal, 1881, pg. 94:
The same gentleman also exhibited a new fine adjustment for microscope stands, invented and manufactured by Messrs. Yawman & Erbe, of this city. What are commonly called fine adjustments rarely get beyond one hundred threads to the inch, but this a differential screw, which is a compound screw by which a motion is produced equal to the difference of the motions of the component screws gives a movement equal to three hundred and sixty threads to the inch. This exceedingly fine movement may be reduced, by loosening a conveniently placed milled-head screw, to sixty threads to the inch, an adjustment sufficiently fine for all low power objectives.

A similar microscope signed by Yawman & Erbe also incorporates this type of differential screw mechanism, albeit with a different fine adjustment construction.

Additional information about the Gundlach businesses in America is online.

See this essay about Ernst Gundlach and his microscopes.

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