532 



SUMMARY OF CURRENT RESEARCHES RELATING TO 



The observer, having removed the ocular, then looks down the tube, 

 aud veil] probably find that the interior of the tube is not uniformly 

 illuminated : small adjustments, in elevation, of the light-source will 

 correct this defect. The function of the lens b is to make the light- 

 rays convergent, so that after incidence on the inclined glass plate 

 (not shown in figure) they may focus on the objective-focus and thence 

 reach the object. Thence they are reflected upwards through the ob- 

 jective to the ocular. The object to be examined (fig. 50) should be 

 provided with two plane-parallel surfaces so that it may lie horizontally 

 on the stage, small differences of level being compensated by the screws 

 S S. The object-stage is provided with two slides, so that the stage 

 may be moved north-south, east-west, by means of the milled-heads 

 T'" T'". The stage is raised and lowered by means of T". If the object 

 is too thick for the stage, the stage can be removed, and either the object 

 be placed on the horse-shoe foot, or the instrument, by relaxation of the 

 screws r r', be swung round and brought (fig. 51, dotted lines) directly 

 over the object. If photomicrographs be desired, the vertical arrange- 

 ment shown in fig. 52 is adopted, a picric-acid filter having been placed 

 in front of the light-source. 



Reichert's New Metal-Microscope.* — This instrument (figs. 53-59) 

 is distinguished from Rejto's Metal-Microscope chiefly in the following 



^^^^gg 



^yyyy^yA 



Fig. 53. 



respects : — 1. By a different mode of light application and by a more 

 complete illumination of the object. 2. By the necessity of preparing 

 only one plane-surface ; this plane-surface being set in contact with the 

 stage. 3. By a specially convenient arrangement for photomicrography. 

 4. By a new fine-adjustment and a lateral screw for oblique inclination. 

 In fig. 53 a schematic representation of the ray-path is shown. The 

 light issuing from the source is brought to the object by means of 

 the prism P x and the objective — this objective thus acting as a con- 

 denser. The light reflected from the object reaches the prism P. 2 , and 

 thence it is deviated through the horizontal tube to the observer's eye. 

 To change over from subjective observation to the photographic fixation 

 of the image, the last-named prism P 2 is rotated 90° about an axis 

 perpendicular to the stage-plane. It will be seen from fig. 56 that the 

 photographic camera is perpendicular to the optical bench carrying the 

 axis of illumination. For convenient observation of the image, an 



* Special Catalogue, Em3, "Metall-Mikroskope,"C. Reichert, Vienna, pp. 1-14. 



