NEUTRAL TINT REFLECTOR. 205 



Another method for the delineation of objects is by the 

 use of the camera-lucida or neutral tint reflector, which by 

 a little practice becomes a very accurate process. The 

 ordinary camera-lucida consists of a prism, and apparently 

 throws down an image of the object upon the paper below it. 



This is the same with the neutral tint reflector ; it is 

 made of a small piece of plate 

 glass, slightly coloured and arranged 

 at an angle of 45 with the eye- 

 piece ; it is shown in Fig. 188. 



There is a fault with nearly all 

 reflectors hitherto made ; the glass 

 is too thick, and consequently two 

 or more images are formed of the 

 object, which come into view by FIG. 188. 



a slight movement of the head. 



To remedy this, a writer in ' Science-Gossip ' proposed a 

 head-rest, but even this may be dispensed with if the glass 

 used be of the same thickness as an ordinary cover, such 

 as is used in the mounting of objects. In the construction 

 of a reflector for drawing purposes, it is only necessary to 

 hold a thin glass cover at an angle of 45 with the eye- 

 glass, in such a position that the centre of the cover coin- 

 cides with the optical axis of the microscope. Surely 

 students interested may manage to do this for themselves. 



When using either the camera-lucida or the neutral tint 

 reflector, the cap is removed from the eye-piece and the 

 accessory placed in its stead, the microscope arranged hori- 

 zontally, and the paper placed under it upon the table, as 

 shown in Fig. 189. 



The instrument shown is one of Messrs. Ross's make, 

 and is nicely balanced in all positions. Messrs. Swift and 

 Son place a stop on most of their stands, so that it is easily 

 known when the body is either horizontal or vertical. 



