MICROSCOPE-ANTIQUES.COM © 2013-24.

COMBINED INVERTED AND VERTICAL COMPOUND MICROSCOPE

MAKER: BAUSCH & LOMB

MODEL:UNIVERSITY MICROSCOPE

SERIAL NUMBER:Unknown*

c. 1886-7

AUTHOR: Barry Sobel

EDITORS: Joseph Zeligs & Paul Ferraglio

*B & L assigned serial numbers to their microscopes, but many examples do not have their serial number noted on the microscope itself.

Please Click On Pictures for a Larger Version Where Available

INTRODUCTION:
As the microscope became an accepted scientific tool, its use expanded to fields like chemistry. Because chemical fumes tend to rise, especially when heated, they can be injurious to the microscope and noxious to the user who was looking down from above! For this reason, inverted microscopes, including those convertible from traditional to the inverted form, as well as those designed to be used only in the inverted position were developed. Bausch & Lomb introduced their two Combined Invertible and Vertical Microscopes in 1886, the Laboratory Model and, as featured on this page, the heavier and slightly more expensiveUniversity model. Both these microscopes are extremely rare today.

DESCRIPTION:
This microscope is supported with a large and heavy, unusually-shaped foot similar to the one supplied with the Bausch & Lomb Concentric model. The finish on the foot, like many B & L stands, is a heavy-duty yellowish coating applied over brass, unlike the rest of the microscope that is lacquered brass. There is a brass drawtube which has a nickel-plated draw measuring 3 2/3 inches (93 mm). The distal end of the drawtube is has a hard rubber end that is threaded permitting to addition of e.g. an erecting lens. The foot has a right to left spread of about 7 inches and the instrument stands about 9 inches tall in the inverted configuration. In the upright configuration it is about 14.5 inches high with the drawtube pushed all the way in, and about 18.5 inches high with the drawtube fully extended.

A single column on the foot supports a joint through which the rest of the microscope can rotate about a horizontal axis to rest in the traditional or inverted configuration. This movement also allows it to be inclined (sideways) when used as a traditional microscope. The tension on this can be adjusted via a spanner wrench acting inserted in the two holes on the screw securing the axis of rotation.

The arm of the microscope contains a rack and pinion coarse focusing mechanism. Fine focus is by threaded screw to the limb acting on the Gundlach type leaf-spring fine focus, originally shown in the 1876 Gundlach patent, and modified as shown in the 1885 Bausch patent, as illustrated to the right.

The prism box has an outside length of about 50.5 mm, the width is about 25 mm. It is about 20.6 mm from the inside bottom to the top edge in the taller portion. The flat portion receiving to image measures about 24.5 mm long and the inclining part where the light exits towards the eyepiece is about 22.5 mm long. A drawing of the prism that was originally provided is shown to the left, and diagrams of the prism are shown on the Invertible Microscope Prism Page.

The prism box is attached to the microscope by a lip and screw arrangement. One end of the prism box has a shallow lip that fits into a narrow slot in the prism box receptacle. Everything is then secured by tightening the small knob of the screw visible at the outboard end of the prism box bracket.

When the microscope is setup in the inverted orientation, the prism box must be installed and the optical tube is screwed into the hole located in the angled section of the prism support bracket. For the traditional vertical configuration, the prism box is removed, and the optical tube is screwed into the hole at the opposite end of the objective.

The brass stage ring encloses a clear glass plate with a central round opening of about 30 mm diameter. The single tailpiece carries the mirror assembly and a cylindrical sleeve for holding substage accessories. Each is on a sepaarate slide and can be adjusted independently. The tailpiece itself can be rotated around a horizontal axis in the plane of the stage in order to bring the illumination apparatus either above or below the stage for inverted or vertical orientations of the microscope. Rotating in the plane of the stage also eliminates the need to refocus the substage apparatus if it is positioned off-axis for oblique lighting. A removable wheel of apertures is presently mounted in the substage ring. The two inch (50 mm) diameter mirror is double sided, convex and one side and flat on the other. It is mounted in the usual gimbal and can be extended parallel in its own separate slide on in the tailpiece.

ACCESSORIES:
The microscope was received with a single unmarked top hat eyepiece and a single 1/4 inch Gundlach objective(shown to the right). It is signed D on one side and 1/4 on the other side and below these Ernst Gundlach. There was a single short lacquered brass extension tube(shown here attached to the objective), between the objective and the prism box bracket that is used to raise the objective sufficiently close to the specimen slide in the inverted configuration; this is needed to bring the front of the objective close enough to the stage to reach focus when in the inverted configuration without the body tube running into the stage. Lacking on receipt were the other extension(s) which are required when using the short focal length Gundlach objective.

All of the accessories now with the instrument are shown to the left. The original wheel of diaphragms is present. Additional B & L extensions of various lengths have been added to allow any of the objectives to be used without damaging the fine focus. Other period B & L objectives have been added in focal lengths of 2 inches, 1 inch, 2/3 inch, 4/10 inch, and 1/8 inch. A suitable analyzer and polarizer have also been added.

The microscope was designed to work with draw tube extended to the 8 1/2 inch American tube length of the time, but could also work with the continental tube length of 6 1/2 inches(166 mm) with the drawtube close to the closed position.

Interestingly, the two patent dates stamped on the focusing block of the microscope are earlier than the patent filing for the microscope itself; Oct 3, 1876 and Oct 13, 1885. These patents refer to the focusing mechanism and predate the patent of the microscope itself (which was in November of 1887). Since this patent was applied for in March of 1887, it is possible this example dates to before that date, since no reference to the specific invertible microscope patent applied for or registered (in 1887) is stamped on the microscope. It is also possible that B & L saw no need to add the date of this direct patent.

CONDITION:
This microscope is in good overall cosmetic condition but were some mechanical problems when it came to me; the Gundlach-type fine focus mechanism was damaged. This likely occurred because the single objective extension was not long enough representing only one part of what was supposed to be a multi-part extension tube. This meant that, when the instrument is in the inverted configuration, as the objective is focused closer to the stage, the angled main optical tube meets the stage which pulls on the leaf spring closest to the objective. This leaf spring was thus pulled out of its solder joint. This defect resulted in the objective not being in the optical axis of the rest of the instrument. After correcting this problem*, this issue was laid to rest. This occurred because the proper extension(s) for the objective are needed to avoid this problem. These have now been added to the microscope. (see image at the bottom of the page).

The missing prism has been replaced by a spare Bausch & Lomb prism somewhat like the original, but it does not transmit light well. The damaged knurling on the fine focus knob shows signs of previous use of pliers to turn it. The threads on the piece it screws into were partly stripped so the fine focus knob would not engage these threads except when almost all the way down. This defect was corrected via replacement of the stripped screw by the eminent instrument restorer, Paul Ferraglio. The inversion process works smoothly and the coarse focus is in good working order. Fine focus now works as originally intended. As noted, the upper leaf spring ot the fine focus has been reinstalled into the slot it fits into and re-soldered in place. Other than the prism in the inverted configuration, all parts now function normally. Original B & Lomb extensions of suitable lengths have been added so that any objective can now be used without a problem.

When received the foot was heavily spotted. The foot has been cleaned and protected without disturbing its original machining lines, remaining coating, and edges. There are scattered lacquer losses on the bright parts of the rest of the microscope. The brass ring of the stage has some lacquer losses around its circumference. The instrument is now in overall very fine condition.

*The spring was placed back in its slot and resoldered. Thanks to Paul Ferraglio for information on how to disassemble it!

HISTORY OF SOME INVERTIBLE CHEMICAL MICROSCOPES:

Inverted microscopes were made by several makers including Plossl, the Chevaliers, and many others. Like the later B & L University Microscope, the Universal Achromatic Microscope of Charles Chevalier, dating to about 1840, was also invertible, though the optical tube would be horizontal in this configuration (left).

Although Charles Chevalier had produced a microscope that could be set up inverted, the dedicated inverted microscope with the tube oriented at a comfortable angle, and specificly developed for work with chemicals, was suggested by the American Professor J Lawrence Smith, who presented it to the Societe de Biologie of Paris in 1850, and then reported it to the American Scientific Association in 1851. He also reported it in the 1852 issue of the Am J Sci Arts. Vol 14: 233-241.

In France, soon after his presentation in Paris, Smith's invention was first sold by Nachet(with a footnote giving credit to Smith) no later than 1852 as shown in the illustration in Quekett's 2nd edition of 1852 of A Practical Treatise on the use of the Microscope, pp 490-492.

In the U.S.A. it was produced by Grunow and offered no later than 1857 as shown in their catalog.

The initial model of Smith's inverted microscope by Nachet continued to be offered in the Nachet catalogs through 1910. But in 1872, Nachet introduced two additional versions of inverted microscopes. These were the New Large Inverted Model (right) and the smaller New Inverted Microscope (left). The latter was ...intended for the studies of anatomical elements in gaseous environments and at constant temperature.Coarse focusing was by turning the objective mount and fine focus was via fine screw to the column supporting the stage. Upon the stage was a circular glass cell with a hole in the bottom covered with a thin glass cover attached via Canada balsam. A glass over plate was supplied to cover the top, to be sealed with glycerin to prevent loss of liquid, or a rubber seal to prevent loss of gas. Metal fittings were present to hold the top glass plate firmly against the cell. The microscope was also supplied with a device to maintain a constant temperature of the cell.

In the 1881 catalog, a slightly different arrangement of a glass cell with provision for fluid to be circulated through it, and sitting on the copper plates for constant heating was supplied. The same was supplied in 1886, 1892, 1898 and 1900, but in 1898 the large model was no longer listed. In 1910 only the original form was listed in the Nachet catalog.

In was in 1886 Bausch & Lomb introduced their combined inverted and vertical microscopes. Patent number 373,634 was issued to Emil Bausch in 1887. This depicted the Laboratory version of it. The B & L invertible microscopes were first reported in the JRMS in 1887 (pp 141-144) and were offered by B & L from 1886 to 1895 during which time the catalog referred to them as the Laboratory model(double column black foot) and the University model(thick single pillar, heavier lead-filled brass foot). The advantage over the inverted microscopes of Grunow 1857 or earlier) and Nachet (as early as 1852 onward) was that unlike these dedicated instruments, designed primarily for chemical work, B & L's forms could easily be converted to a traditionally oriented (vertical) microscope, thereby allowing subjects to be seen both from below and above. As noted below, this idea actually originated with Charles Chevalier, but because of the angled tube, (rather than horizontal tube in Chevalier's microscope), B & L microscopes were much easier to use. This then might appeal to a wider audience, and certainly reduced the need for a second microscope for ordinary work. The biggest disadvantage of the B & L design was the use of the wear-prone Grunow leaf spring fine focus mechanism which frequently failed.

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Image courtesy, and collection of, Dan Kile.
Click Image to Enlarge.

An example of the laboratory model is shown here(courtesy and collection of Dan Kile). The B & L University microscope featured at the top of this page is identical to the B & L Laboratory Microscope (left) of the same period except for the University Model having (1)a thick single support pillar instead of two, (2)a larger and heavier foot, and (3)a brass finish throughout (though the foot was not bright-lacquered). After 1895 B & L no longer listed invertible microscopes in their catalogs; they then, confusingly, made an entirely different microscope also called the Laboratory model, which was of the traditional form, and not invertible, and the University Microscope (not to be confused with their Universal microscope,) was no longer offered.

Inverted microscopes are still made today, though they are now more commonly used to look at heavy opaque objects like meteorites, and the bottom of cell culture containers.

One of the most ingenious portable microscopes, invented by the Englishman John McArthur, uses an inverted design and the McArthur types of microscopes are reviewed elsewhere on this site.

From the 1893 B & L Catalog:

The author is grateful to Paul Ferraglio for additional suggestions regarding this web page