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. Shding 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 

 ^licroscope, differing in some respects from that just 



Fig. 44. — Baker's Educational Microscope. 



