J. Swift & Son, Dick Model Petrographic Microscope, ca. 1890

 

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. 

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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