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Description: | none MANU W. Watson & Sons Ltd. circa 1935 313 High Holborn, London, England DES after NICOL,William. 1838 Edinburgh, Scotland. DES after MALUS,Etienne,Louis. 1808 Paris, France. DES after HERAPATH,William,Bird. 1852 Bristol, England This is a Watson microscope J sheet polarising filter that was probably an accessory for a "Patna" model microscope. It is a very early polaroid type filter based on Edwin H. Land's herapathite (iodoquinine sulphate) polarising filters presumable imported by Watsons. It is part of a boxed set consisting of; this in line 12mm filter in a rotatable attachment , which was placed between the objective and the eyepiece of a microscope and a stationary 35mm filter that was inserted into the substage lens assembly.
Land's J filters were made by squeezing a colloidal dispersion of the needle like crystals of herapathite in nitrocellulose through a narrow slit that forced them into a parallel alignment. The material was then dried to form a thin sheet This created a filter that mimicked what had hitherto been impossible to achieve, a large single crystal of herapathite. Herapathite is an olive green colour and is a magenta dichroic i.e. as a colloid it apppears to be a pale buffy-green colour when placed on a sheet of white paper but when the filters are rotated, in respect to one another to the extinction point, the transmitted light becomes magenta in colour. This is because the green light from the visible spectrum is reflected by the filter and only the blue and red passes through it. | License: | http://www.hmag.gla.ac.uk/spirit/rights/ | Publisher: | Hunterian Museum and Art Gallery, University of Glasgow | Rights holder: | Hunterian Museum and Art Gallery, University of Glasgow | Subjects: | SCIENTIFIC COLLECTION : | Source: | Hunterian Museum | Creator: | Hunterian Museum and Art Gallery, University of Glasgow | Identifier: | http://www.huntsearch.gla.ac.uk/cgi-bin/... | Language: | en-GB | Go to resource |
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