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Objectives whose settings are so matched that they are ap- 
proximately in focus when changed can, by means of the clamping 
screw on the objective slide, be fociissed accurately and then 
fixed once for all in their proper position. The two pieces fit one 
another accurately; any number may be supplied with the tube- 
slide in the first instance or subsequently. 
On changing the objectives with a properly adjusted changer 
the same part of the object always occupies the field, the object 
being so nearly in focus that only a slight adjustment by the 
micrometer screw is necessary. 
Tube-slide 
Objective slides, each 
We supply special cases for these changers, viz: 
a) Case for 3 objective-slides 
ena. 
