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An Improved Form of Dr. Edinger's Projecting Apparatus. 

 By E. M. Nelson, F.R.M.S. 



(Read November \Uh, 1892.J 



This instrument, which has been made for me by Mr. Curties, 

 is similar to that suggested by Dr. Edinger in the " R M.S. 

 Journal," 1891, p. 812. I have, however, made one or two 

 trifling alterations, by which an increase in the illumination of 

 the image is secured, which adds to its efficiency. It consists of 

 an upright brass rod* holding a short horizontal tube, at the 

 end of which a mirror is placed at an angle of 45°. Below this, 

 for a condenser, is fitted one of my aplanatic bull's-eyes, the 

 elements of which can be used either singly or together as 

 occasion requires. The stage, which is also horizontal, is 

 placed below the condenser, and is fixed to a separate piece, 

 which carries also the projection lens with its rack work. 

 This arrangement permits both the stage and projecting lens 

 to be together moved from the condenser, while the projecting 

 lens has an independent movement to and from the stage. A 

 wheel of diaphragms is placed above the stage. The source of 

 illumination should also have an aplanatic bull's-eye, and should 

 be one foot distant from the condenser. 



This instrument not only shows low power objects very 

 e;ffectively, but also is most nseful for drawing them. As the 

 image is inverted and transposed the drawing will be precisely 

 like the original. 



* The brass rod has since been altered to a wooden board. 



