ZOOLOGY AND BOTANY, MICKOSCOPY, ETC. 



85 



board is correct. A sheet of paper with a series of concentric circles 

 drawn upon it will enable the question of the circular outline of the 

 field to be readily settled. Such a sheet of paper is also useful for 

 determining whether the line of sight is vertically downwards when the 

 camera is used to project the image upon the table. 



If the camera is used not only with low-power, but also with 

 moderately high-power eye-pieces, the mirror must be so arranged that 

 its free end, when the mirror is inclined at about 45°, is as close as 

 possible to the eye-lens. This can only be done by making the mirror 



Fig. G. 



rather small and pivoting it to the front plate just above the central 

 opening in the latter. After several trials it was found that a small 

 cover-glass, say, about half-an-inch in diameter, silvered on one side 

 and cemented to a thin metal plate, gives excellent results, and seems 

 altogether the simplest and most suitable form of mirror for this 

 camera. 



As regards the neutral tint glass, it is necessary to make it rather 

 large, because, owing to the adjustments which have to be made for 

 various inclinations of the Microscope, the light is not always reflected 

 from the same spot. Moreover, it is evidently essential that the whole 



