9 6 



ELEMENTARY CHEMICAL MICROSCOPY 



In the Reichert instrument the illuminating and image-forming 

 rays take the directions indicated in Fig. 46. The light rays from 

 a radiant R enter the tube V, pass through a condensing lens 

 and are twice reflected by the prism P. Passing through the 

 objective O, a spot of bright light is formed upon the surface of 

 the inverted preparation M lying upon the stage S. The surface 

 of M reflects the rays downward through O to the prism PI, 

 thence the image-forming rays are reflected in the direction E 



FIG. 46. Path of Light Rays in the Reichert Metallurgical Microscope. 



through the body tube T of the microscope which carries at its 

 outer end an eyepiece of the usual construction. Owing to the 

 space required for mounting PI, the tube length of the micro- 

 scope is greater than usual and objectives corrected for a tube 

 length of not less than 200 millimeters must be employed. 



The prism PI is so mounted that it can be rotated through an 

 arc of 90 degrees by means of the milled head K. To K is at- 

 tached an indicator I which marks the position of the reflecting 

 surface. In the position of I shown in the diagram the image 

 formed by the objective is sent to the observing tube of the 

 microscope; turned through 90 degrees the rays are reflected 

 into the tube indicated by the dotted circle C, whose axis is at 

 right angles to that of T. The tube C is fitted with a projection 

 ocular whose function it is to form an image upon the ground 



