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KECOKD OF CUKRENT EESEARCHES RELATING TO 



a swivel joint, the swivel accommodates for any difference of length 

 in the points and thus equalizes the pressure and prevents slipping. 

 The stage is thin enough to admit an angle of 160 degrees. 



The substage is made in two parts, intended for the examination 

 of polarizing objects when using an achromatic condenser. The 

 lower part has a motion to one side, which leaves the condenser and 

 light from the mirror in the same position. Fig. 140 shows the 

 lower part swung out. 



The Gillett diaphragm to the condenser — placed above the lenses — 



Fig. 141. 



is also shown, and a convenient plan for mounting a hemispherical lens 

 for immersion illumination attached to an elbow-piece beneath the 

 stage. 



(3) Biological. — This (Fig. 142) is a smaller and more recent 

 instrument (patented in 1879). 



The substage and mirror can be moved indei^endently round the 

 focal point as a centre, and can be used above the stage if required. 



