88 



THE MICROSCOPE. 



thickness of an object or the thin covering-glass. The 

 other milled-head fixes the arm to the square bar. Below 

 the table-stage is the secondary or sub-stage, into which is 

 fitted the diaphragm, polariscope, achromatic condenser, 

 and other illuminating apparatus. It is supplied with 

 centering screws, circular and focussing rack-work, giving 

 perfect and accurate adjustments. Sliding upon the lower 

 end of the instrument is a large double mirror, with 

 double-jointed arm, and above this a full-size Amici prism 

 for oblique illumination. The microscope is furnished with 

 a draw-tube, divided into tenths of an inch, and is thus 

 rendered as perfect as is necessary for all purposes. 



Fig. 43 represents Mr. Baker's smaller Compound 

 Microscope, differing in some respects from that just 



Fig. 44. Baker's Educational Afimwcope. 



