LABORATORY AND TEACHING METHODS 



58s 



Table of Micrometer Values. — {Contiuued) 



Designation of j Focal length, 

 objective 1 mm. 



100 intervals of the step 



A/r^,i ^t „,\^;^u micrometer covers as 



th^'e dtw\ute'has —/ -*— ^^ °f ^^e ob- 



V u^ a-.^Z^i-Ja I ject micrometer as men- 



to be adjusted tioned below, (i interval 



equals Moo mm.) 



Oil 



immersion 

 K2ff 



Oil 

 immersion 

 Vie 



4.2 

 3-2 

 30 

 2.6 

 2.2 



1.6 



Micrometer 

 value in 

 microns 



(o.ooi mm.) 



Fluorite system 



180 

 180 

 152 

 13s 

 168 



158 



165 



Apochromats 



2.0 

 i-S 



i-S 

 1-5 



Step Micrometer 



The special features of the step micrometer (Stufenmicrometer) are that ten 

 intervals constitute one group. Each group is marked partly in white and partly 

 in black. The black groups are accompanied by a white and the white groups by 

 a black figure. These two different markings facilitate considerably the measure- 

 ments of specimens of the opposite color. The grouping of ten intervals to one 

 distinct group allows a rapid and convenient count. The value of one interval of 

 the step micrometer is 0.06 mm. 



Directions (Fig. 208). — Object micrometer i mm. divided into 100 parts to be 



