10 A LABORATORY MANUAL OF BOTANY 
ined. The object must be very small, or if large small 
pieces must be used, since the light must pass through them. 
Place a drop of water on the glass slide somewhere near 
its center, and in this place the object. Take one of the 
cover-slips with the forceps and let it down upon the mount, 
one side going down first, and the other slowly following, in 
order that all air-bubbles may be excluded. Place the slide 
on the stage, with the object directly above the diaphragm 
opening. By looking into the eyepiece make sure the mirror 
is so placed as to reflect the best light. Then with the low- 
power objective in position for use, lower it until it almost 
touches the cover-slip, and while again looking into the eye- 
piece slowly raise the objective by using the rack and pinion 
until the object comes into view.t_ The object is then said 
to be in focus, and may now be studied. When the object is 
once in focus the fine adjustment should be brought into 
constant use in order that the various parts of the object 
may be observed. When higher magnification is desired 
the high-power eyepiece and objective may be used. The 
high-power objective when in focus is so near the cover-slip 
that great care must be used in adjusting it, else it may 
become injured. It will be necessary to turn about the 
nose-piece or lower the tube slowly and carefully, to pre- 
vent the glass from striking the cover-slip. 
Care.—A soft cloth or chamois skin should be at hand 
for removing finger prints or dust from the metal part of 
the microscope, and for cleaning the mirror and eyepieces. 
Objectives needing attention should always be reported to 
the instructor in charge. No dirt or moisture should be 
1 While using the microscope both eyes should be kept open. Con- 
stantly closing one eye often results in serious injury to it, the one 
used being in much less danger. Preferably one should use the eyes 
alternately. If one has trouble in seeing through the microscope 
with both eyes open, the hand may he held over the eye not in use un- 
til such trouble is removed. 
