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GRAND VAN HEURCK MICROSCOPE (Traviss Expanding Dark-Ground Stop)

c. 1910


Traviss Stop Traviss Stop


stop As an alternative to the fixed stops, is the 'Dark-Ground Expanding Stop' originally called a 'Expanding Spot for Dark Ground Illumination' also known as a 'Traviss Stop'.   W. R. Traviss first exhibited this device at the December 1906 meeting of the Quekett Microscopical Club and it was subsequently reported in the February 1907 edition of 'Knowledge & Scientific News' and in more detail on pages 362-364 of the JRMS for 1907. This stop fits the filter holder for the smaller diameter fittings of the 'Holos Oil Immersion Condenser' and the Aplanatic Low Power Holoscopic Condenser.' of the Grand Van Heurck Microscope in this collection.

traviss stop The aperture can be varied from about 5/16 to ½ inches; this range is smaller than the two sizes quoted in the 1912 catalog. With smaller diameters, this stop is suitable for a higher power range of objectives than the larger diameter ranges in the 1912 catalog. One would conceivably need both this one and the larger range example to be able to provide appropriate stop sizes for a wide range of objectives.