he negative. Fig. 153. Focusing Class. It is achromatic, con-sisting of a double convex crown lens and a negativemeniscus flint lens cemented together. It screwsinto the brass tube and is thus adjustable, enablingone to focus the pencil mark in the clear area of thefocusing screen (Fig. /50) with… … S 338. Labeling and Care of Negatives.—The care, printing, etc.,of negatives is like that of ordinary negatives. It is well to label them 198 PHOTO MICROGRAPHY. [CH VIII.
Microscopy
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