Word: oculars
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Dates: during 1880-1889
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...comparative independence of a microscopist from an elaborate stand arises from the fact that the true value of his work is due to his experience and the magnifying power of the lenses which he uses. The objective, or system of lenses nearest the object, and ocular or system nearest the eye, are the two parts upon which this magnifying power depends, the burden of the work always being put upon the objective...
...this country and in England the objectives and oculars are named in inches or fractions of an inch, relatively to the focal length of a simple lens which will produce the same magnification. Thus taking the focal length of the eye as ten inches, a one inch objective magnifies ten diameters, a 1-50 inch objective, five hundred diameters; a 1-100 objective, one thousand diameters; (the highest powers made). When the ocular system is added, the magnification is equal to the product of the magnifying powers of the objective times the ocular. For instance, a two inch vocular...