Remedy.—Keep all lenses scrupulously clean. For cleaning, use well-washed linen (an old handkerchief) or Japanese lens paper.
Eyepieces.—To find impurities, revolve the eyepieces during the observation; breathe upon the lenses, and wipe gently with a circular motion and blow off any particles which may adhere.
Dry Objectives.—Clean the front lens as described. To examine the rear and interior lenses use a 2-inch magnifier, looking through the rear. Remove the dust from the rear lens with a camel’s-hair brush.
Oil Immersion Objectives.—Invariably clean the front lens after use with moistened linen or paper, and wipe dry.
In applying oil examine the front of the objective with a magnifier, and if there are any air bubbles, remove them with a pointed quill, or remove the oil entirely and apply a fresh quantity.
LETTERS, TO REMOVE FROM CHINA: See Cleaning Preparations and Methods, under Miscellaneous Methods.
LETTER-HEAD SENSITIZERS: See Photography, under Paper-Sensitizing Processes.
LETTERING
CEMENTS FOR ATTACHING LETTERS ON GLASS: See Adhesives, under Sign-Letter Cements.