94 CARE OF THE EYES [Cn. Ill 



soft dry cloth or lens paper should be as rapid as possible, so that none 

 of the liquid will have time to soften the setting of the lenses. 



(7) Shellac Cement may be removed by the paper or a cloth moist- 

 ened in 95% alcohol. 



(8) Brunswick Black, Gold Size, and all other substances soluble 

 in chloroform, etc., may be removed as directed for balsam and damar. 



In general, use a solvent of the substance on the glass and wipe it 

 off quickly with a fresh piece of the cloth or lens paper. 



It frequently happens that the upper surface of the back combina- 

 tion of the objective become dusty. This may be removed in part 

 by a brush, but more satisfactorily by using a piece of the lens paper 

 loosely twisted. When most of the dust is removed some of the paper 

 may be put over the end of a pine stick (like a match stick) and the 

 glass surfaces carefully wiped. 



CARE OF THE EYES 



160. Keep both eyes open, using the eye-shade if necessary (fig. 

 56), and divide the labor between the two eyes, using one eye for a 



FIG. 56. EYE-SHADE FOR THE TOP OF THE MICROSCOPE TO ENABLE THE 

 OBSERVER TO KEEP BOTH EYES OPEN. 



while and then the other. It frequently happens that one eye is much 

 more perfect than the other, then of course the more perfect eye is 

 used all the time. 



