120 



SUMMARY OF CURRENT RESEARCHES RELATING TO 



The novelty consists in the introduction of the tinted glass plates * 

 rrr in the path of the rays from the mirror. Also the upper part 

 of the apparatus (mirror p, its arm a, the glasses r r r, and the plate 

 s) is movable on the pivot q upon the lower plate, which forms part 

 of the tube li fixed to the eye-piece by h. 



Millar's Multiple Stage-plate. — The object of this stage-plate 

 (fig. 19) is to facilitate the exhibition of a series of slides so that 

 they may be observed successively without having to remove and 

 replace each object separately. 



The base-plate slides on the stage after the upper stage-plate is 

 taken off, and it holds six slides. Each of these is fixed by two small 



Fig. 19. 



screws (passing through the two longitudinal bars) which press the 

 slide against springs attached to the base-plate, there being six springs 

 beneath each bar. The base-plate can be readily pushed in either 

 direction by the hand when it is desired to examine a different object. 

 The mechanical movements of the stage will bring various parts of 

 an object into the field, but it is easy to adjust each slide on the 

 plate in the first instance so that the object shall be central with the 

 optic axis, there being sufficient spare room to move the slide both 

 laterally and vertically. 



Stewart's Safety Stage-plate, — This very simple device (fig. 

 20) was designed by Mr. C. Stewart to provide an economical but 



Fig. 20. 



effective arrangement for protecting slides from breakage when being 

 exhibited under high powers to large classes of students. 



It consists of a wooden slip the length of an ordinary slide and 



* See this Journal, iii. (1883) p. 119. 



