136 



Where the graduated draw-tube is provided bring 

 the proper figure, either 216.0 or 160.0 mm., in line 

 with the upper end of main tube, in accordance 

 with the tube length to which the objectives are 

 corrected. 



Attach low power eyepiece. 



Attach low power objective. 



Place object on stage. 



Illuminate object. 



Focus on object. 



If the instrument is used in the upright position, 

 place the base close to the edge of the table ; if in- 

 clined, it may set farther in. Rest the arms, as 

 much as the height of the instrument will permit, 

 upon the table. 



How to Work.- -It is now supposed that the 

 instrument is ready for work. To start, it is well 

 for the beginner to provide a few prepared speci- 

 mens, as these will help him considerably if it is 

 his intention, as it should be, to prepare them 

 later himself. If only a portion of the object can 

 be seen and it is desired to see a larger surface, 

 the length of tube may be contracted by means 

 of the draw-tube. In this case the object will be 

 placed out of focus and another adjustment be- 

 comes necessary. If a higher power is desired 

 the draw-tube may be extended. Observe whether 

 the field is well illuminated and if not bear in mind 

 what has been said about properly adjusting the 



