The microscopist : a manual of microscopy and compendium of the microscopic science : micro-minerology, micro-chemistry, biology, histology, and pathological histology / by J.H. Wythe.

Joseph Henry Wythe

Date:: 1877

Credit: The microscopist : a manual of microscopy and compendium of the microscopic science : micro-minerology, micro-chemistry, biology, histology, and pathological histology / by J.H. Wythe. Source: Wellcome Collection.

Provider: This material has been provided by the Francis A. Countway Library of Medicine, through the Medical Heritage Library. The original may be consulted at the Francis A. Countway Library of Medicine, Harvard Medical School.

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$divided is said to be i^olarized^irom. a fancied resemblance to tbe poles of a magnet. The division of the vibrations may be effected [i. t'., the light may be polarized) in vari- ous ways. For the microscope the jjolarizer is a Nichol's prism, composed of a crystal of Iceland spar, which has been divided and again cemented with Canada balsam, so as to throw one of the doubly refracted rays aside from the field of view (Fig. 22). Such a prism is mounted in a short tube and attached to the under side of the stage. In order to distinguish the effects of polarized light, an analyze}^ is also needed. This usually consists of another Fig. 22. Fig. 23. Kichol's Pi ism. Polarizer and Analyzer. similar l^ichol's prism, attached either to the eye-piece or just above the objective. The latter position gives a larger field, but the former better definition. Fig. 23 shows the polarizer and the analyzer. The polarizer is improved by the addition of a convex lens next the object. Hartnack has also improved the eye-]3iece analyzer by adding a graduated disk and vernier. When the polarizer and analyzer have been put in place, they should be rotated until their polarizing planes are parallel, and the mirror adjusted so as to give the most intense light. If now the polarizing planes are placed at right angles, by turning one of them 90°, the field is ren-$