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Early Petrographic Microscopes

Petrographic microscope by R. Fuess after H. Rosenbusch, Berlin, ca. 1875

 

This is the first true microscope for petrographic purposes.  Rudolf Fuess, Berlin, made it according to the specifications of Prof. Harry Rosenbusch of Strasbourg.

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In the publication of "New Yearbook for Mineralogy" in February 1876, Rosenbusch made the following demands in his article on that revolutionary instrument entitled "A new microscope for mineralogical and petrographic investigations":

1) With fixed crossed Nicols, one must be able to comfortably rotate the examined object centrically in its own horizontal plane.

2) One must be able to read with desirable accuracy the angle through which an object has been rotated in the horizontal plane.

3) the planes of vibration of the Nicols must have a known position that can easily be restored at any moment after any displacement that has been carried out.

4) Where the adjustment to the maximum of the extinction cannot be carried out with the necessary sharpness due to some circumstances with ordinary white light, one must be able to make use of sharper methods conveniently.

This microscope bears no serial number. According to Prof. Ing. Timo Mappes, it was not until the late 1870s that the company's microscopes were consistently signed and numbered. It was bought from a dealer in California but with no clear provenance. It is very unusual to find such a microscope in the USA, as these early petrographic microscopes were very German and, after their introduction in ~1875, were quickly replaced, by the 1880s, by later models. Unless it was brought to the USA by another collector, the only geologist who performed in the USA any sort of petrographic study (a discipline that was still in its birth) was Ferdinand Zirkel, a professor of Geology from Leipzig whom the US government hired to come to the United States in 1874 to examine the great collections of minerals made during the Geological Exploration of the Fortieth Parallel. However, based on the evidence at hand, we cannot go that far as to suggest that this was his microscope. 

Prototype petrographic microscope(?) ca. 1875-1880

 

This is an early form of a petrographic microscope. It consists of blackened and nickel-plated brass and steel, and the horseshoe is made of black-lacquered zinc alloy. The upper optical and focusing systems are constructed on a steel prism column erected from the stand holding both the stage and the horseshoe base. Two optional methods can make the coarse focusing adjustment: either by sliding the tube into its sleeve, where it can be anchored by a small knurled knob screwing into the sleeve, or with the rack and pinion movement based on the prismatic column. Above all, this large stroke is designed to test unusually thick samples.

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The rotating stage is unique. It can be turned very smoothly by only one finger due to a kind of rough dentation of the edge. The outer ring of the circular stage is marked with 360°. Against it and for measuring purposes (of the angle of extinction, the angles of Carlsbad twinning, etc.), a rectangular engraved division is placed on the stage holder.

The tube diameter for accepting the ocular (and therefore also the ocular diameter) is 30mm, unlike the usual 23mm, the common diameter used by makers in France and German countries. At the same time, the objective thread is RMS standard. When the microscope was purchased, it came with an early 20th-century unsigned objective, which was replaced for the sake of the photos seen here with a contemporaneous A objective by Carl Zeiss, Jena. 

Apart from the original objectives, this microscope is undoubtedly missing some of its other components. A screw connected to the lower side of the stage holder was most likely intended to hold a substage sleeve for a Nicol-prism polarizer. As in other early petrographic microscopes, the analyser must have been another Nicol prism set within a goniometer and assembled on top of the ocular eyepiece. Similar attachments can be seen on the early petrographic microscopes by Rudolf Fuess of Berlin, made for Prof. Harry Rosenbusch.

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The identity of the maker of this interesting unsigned microscope is enigmatic. To the best of our knowledge, there are no records of any similar instrument in any other collection. By many features (the stand, the base, and especially the circular dentated stage and its holder), it is similar to the early models made by Fuess and Rosenbuch. However, it is probably not one of their products. It may be a one-off factory prototype, but due to the lack of any written records known to us so far, this assumption remains highly speculative. There is some doubt whether it was designed as a petrographic microscope, as there is no flange above the eyepiece to place and index a graduated cap analyzer. There is no provision for the centration of the objective or stage, nor is there a provision for any waveplate.  Thus, despite some similarities to Fuess instruments, it may also be interpreted as a primarily biological microscope with a rotating stage.  Or, it could have been a special-purpose microscope built on special order.  

The author would like to gratefully acknowledge the kind assistance of Dan Kile, PD dr. Timo Mappes, and Dr. Joe Zeligs for fruitful discussions and their views concerning this microscope.

 

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Petrographic microscope by Constant Vérick, ca. 1885, used by pioneers of petrography

 

This is an unrecorded form of a polarizing microscope attributable to Constant Vérick.
The microscope bears, on the stand, the provenance of:
Laboratoire d'histoire
naturelle des corps inorganiques
Collège de France

Or in its full name: Laboratoire de Géologie physique et chimique attaché au cours d'Histoire naturelle des corps inorganiques du Collège de France.

So it comes from the laboratory of Ferdinand André Fouqué (1828 – 1904), who worked jointly with Auguste Michel-Lévy (1844 – 1911) on the artificial production of feldspar, nepheline and other minerals, and also of meteorites, and produced "Minéralogie micrographique: roches éruptives françaises" (1879) and "Synthése des minéraux et des roches" (1882). At the age of twenty-one Fouqué entered the École Normale Supérieure in Paris, and from 1853 to 1858 he held the appointment of keeper of the scientific collections. In 1877 he became professor of natural history in the chair of geology at the Collège de France in Paris. In 1881 Fouqué was elected a member of the Academy of Sciences. He was the first to introduce modern petrographical methods into France. Fouqué is also noteworthy for his pioneering archaeological excavations on the island of Santorini, where in 1862, during geological excavations, "M. Fouqué had brought to light a whole civilisation buried beneath a layer of pumice-stone, due to an eruption supposed to have happened about 2000 B.C. He found walls coated with stucco, and painted with stripes and floral decorations, hand-made and wheel-made pottery; in short, the relics of a civilisation which we should now call 'Mycenæan ("The Dawn of Greece", The Quarterly Review. 194: 218–243. July 1901; quote pp. 219–220).

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J. Swift & Son, Dick Model Petrographic Microscope, 1891, owned by Prof. O.T. Jones, FRS, FGS

 

For a collector of petrographic microscopes, the Victorian-era microscopes in England are beautiful, but of lesser interest. Although they were provided with polarization equipment early on - for example, since 1870 - and are often offered as polarization microscopes, they are not really. For the salon microscopists, who wanted to see colorful polarization-optical phenomena in the search for the evening kick, they were well suited, but not for quantitative scientific work. An exception is undoubtedly the petrographic microscope by AB Dick, whose principle he described in 1889 and which was conducted in 1891 in the catalogs of the company Swift & Son. It came up with a completely different and innovative technique. 

A good review of the Dick microscope and its history is presented by microscope.antiques. For mineralogical work with the polarizing microscope, a defined and precisely measurable rotation of the specimen relative to the position of the polarizers is absolutely necessary. Classically, it uses a graduated turntable, but this means that you have to adjust the mechanical axis of rotation of the microscope stage and the axis of the imaging optics to each other for each individual lens. What today is standard with centering turrets was a major mechanical challenge at the time of the early development of polariscopes, which was solved differently by different companies. AB Dicks innovative approach was a synchronous rotation of the polarizers in a stationary preparation. This was an exactly manufactured, well-stored turntable dispensable and the annoying centering of the lenses especially at high magnification accounted for. Even with the use of additional equipment, such as the universal turntable, this synchronous rotation was advantageous. It was therefore adopted by virtually all the major microscope makers for their large research stands, but mostly in combination with a turntable, so that, depending on the objective, both methods could be used.
The synchronous rotation of the polarizers in the classical Dick microscope is done via a gear transmission and a long pinion rod as coupling between polarizer and analyzer, as it was taken over and improved by Fuess for the large tripod VI. Other companies have developed the principle in the form of closed gearboxes and a better coupling such as Voigt & Hochgesang (later continued by Dr. Steeg & Reuter) and Leitz.

Allen B. Dick first described his design for a polarizing microscope in the Journal of the Royal Microscopical Society (RMS, 1889, pp.432). In this design the stage remains fixed, while the polarizer and analyzer rotate in synchronism by gearing with an angle scale readout on the stage. The microscope was manufactured and signed by J. Swift & Son of 81 Tottenham Court Rd., London (Swift Catalog, 1891). The instrument became known as the Dick Model featuring an English foot with a Traviss rolling slide holder.

This c.1891, English, signed to foot ‘J Swift & Son, London’. There is also the Initials O.T. Jones on top of the box and also engraved on one of the foot stands. Also the word “Lacey” in italics. Standing on large cast brass foot finished in lacquered and anodized brass, trunnions at top support body, large plano-concave mirror on gimbal below substage, substage assembly with rotating Nicol prism on fold out arm, iris diaphragm and focusing condenser all on rotating divided circle for angular measurement, square stage with Swift 2″ patent mechanical stage and main body to rear of stage incorporating the ‘Dick’ rotating mechanism with fine focus via screw and course focusing via diagonal rack work, body tube incorporating a sliding plate with wheel of apertures and slide in/out Bertrand lens, to top a rotating and folding analyzer engraved with 45 degree positions, complete with five Swift objectives, three eyepieces and one blank, bullseye condenser, and other accessories.

Owen Thomas Jones, FRS FGS (1878-1967) was a Welsh geologist. He was born in Beulah, near Newcastle Emlyn, Cardiganshire, the only son of David Jones and Margaret Thomas. He attended the local village school in Trewen before going to Pencader Grammar School in 1893. In 1896 he went up to University College, Aberystwyth, to study physics, graduating in 1900. He then went to Trinity College, Cambridge, and was awarded a B.A. degree in Natural Sciences (geology) in 1902. In 1903 he joined the British Geological Survey, working near his home in Carmarthenshire and Pembrokeshire. In 1910 he was appointed the first professor of geology in Aberystwyth. In 1913 he became professor of geology at the University of Manchester, and then, in 1930, Woodwardian Professor of Geology at the University of Cambridge (until 1943). He dedicated his working life to the study of Welsh geology.

In 1926 he was elected a Fellow of the Royal Society. In 1956 he was awarded the Royal Medal of the Royal Society, and on receiving it he was described as 'the most versatile of living British geologists'. The same year he was awarded the Wollaston Medal and the Lyell Medal of the Geological Society of London. He was twice president of the Geological Society.

He died at the age of 89 having produced more than 140 publications. A year before his death he published a paper describing the Welsh source of the bluestones of Stonehenge (written in Welsh).

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Owen Thomas Jones, FRS FGS (1878-1967)

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References: MHS 55102

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