Abstract
LONDON. Royal Microscopical Society, October 16.—Dr. J. W. H. Eyre, vice-president, in the chair.—Mr. Taverner exhibited a number of stereo-photomicrographs of water mites, taken with a stop behind the objective, as described before a previous meeting. They were taken in their natural colours by the Sanger Shepherd three-colour process.—Ghost images in the secondaries of Coscinodiscus asteromphalus, with some remarks on the highest useful ratio of magnifying power to aperture: A. A. C. E. Merlin, In an experiment suggested by some remarks of Mr. Nelson, the author was able to distinguish perfectly well-defined ghost images of the condenser stop in many of the cap perforations of Coscinodiscus asteromphalus. He used a selected Zeiss 3 mm. apochromat of N.A. 1.42 and a 40 ocular in conjunction with a Powell's dry apochromatic substage condenser. The exact size of the perforations was measured and found to be 1/83,300-inch.—A new prismatic ocular: A. A. C. E. Merlin. The author found that prolonged observations with the microscope in an upright position entailed great fatigue to the eye, and it occurred to him that by means of a properly designed prism a comfortable position might be secured. He obtained the assistance of Mr. E. M. Nelson, who computed a prism of the kind required, a diagram of which was drawn on the blackboard. It was constructed for the author by Carl Zeiss, and has proved efficient and satisfactory in use.—A new 1/6-inch semi-apochromatic objective: E. M. Nelson. The objective had a working distance of 1 mm. its N.A. was 0.74, and its initial power 60.—Systematic exposure with transmitted light in photomicrography; A. Letherby.
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Societies and Academies . Nature 77, 46–48 (1907). https://doi.org/10.1038/077046a0
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DOI: https://doi.org/10.1038/077046a0