is used, use the low power objective as a finder 

 then swing the high power objective into position, 

 care being taken not to touch the slide, and focus in 

 the manner to be described. The object may not be 

 in the field, due to a slight variation in the centers of 

 the objectives, but it will certainly be very close and 

 ought to be easily found. 



The mechanical stage in either the fixed or attach- 

 able form will be found to greatly facilitate work in this 

 direction, particularly if the object is minute and if in 

 an important investigation one desires to be absolutely 

 convinced that the whole field has been covered, as for 

 instance in the search for bacilli. 



To Illuminate the Object. This is an 

 extremely important feature and should always be 

 carefully done, as one may easily fail to obtain the 

 best results, may be led to wrong conclusions, or may 

 injure the eyes. 



The mirrors of the microscope are usually plane 

 and concave and are provided with universal joint, so 

 as to reflect the light from any source in front or at 

 the side of the microscope. 



The plane mirror, Fig. 46, reflects the light in the 

 initial intensity of its source and is used with low 

 power objectives. The concave mirror, Fig. 47, con- 

 centrates the rays on the object and thereby gives 

 intensified illumination and is used with medium and 



