APPENDIX I 671 
which means that the lenses are in focus. (If two objectives 
only accompany your instrument, the low power is the shorter 
one.) The object, if not under the lens, may now be brought 
into the field by moving the slide back and forth very slowly 
while looking through the ocular. To improve the focus, 
slowly turn the fine adjustment screw. 
7. To focus with the high-power objective, first find the 
object with the low power and arrange in the center of the field. 
Put clips on slide without moving it. Raise the body tube by 
means of the coarse adjustment. Then turn the high-power 
objective into position. Lower the body tube carrying the 
objective until the objective front lens nearly touches the cover 
glass. A slight movement of the fine adjustment should show 
the object clearly. Never focus down with the high-power 
objective while looking through the ocular because of the danger 
of pressing it into the cover glass and the risk of ruining the 
delicately mounted lenses. 
Accustom yourself to use both eyes indifferently and always 
keep both eyes open. If right handed, observe with the left eye, 
as it is more convenient in making drawings. 
9. When the oz/ immersion objective is to be used, a small drop of 
immersion oil (slightly evaporated cedar oil) should be placed on 
the cover glass directly above the object, and the body tube 
should be run down with the coarse adjustment until the. front 
lens of the immersion objective enters the drop and comes almost 
into contact with the cover glass. This should be done while 
watching the objective. Then look through the ocular and 
draw the objective up with the fine adjustment until the object 
comes into focus. 
RULES FOR THE CARE OF THE MICROSCOPE 
1. In carrying the microscope to or from your table, grasp it 
firmly by the pillar and hold in an erect position, so that the 
ocular which is fitted loosely into the draw tube may not fall out 
and its lenses become damaged. 
2. Never allow the dry objective to touch the cover glass or 
the liquid in which the object is mounted. 
