MR. WEN HA M*S REFLEX ILL UMINA TOR. ^ I 



pencil of light can be projected on to the object more perpen- 

 dicularly than with the bull's-eye condenser, thus preventing 

 shadows in coarse or deep objects which often produce dis- 

 tortion and false appearances. When the apparatus is 

 used for opaque objects with a lower power than the i-inch 

 objective, the achromatic combination can be removed and 

 the light directed from the prism, which can be made to 

 give convergent rays sufficient for use with a 4-inch 

 objective. 



Wenham's reflex illuminator is valuable for use with 

 high powers ; but it possesses the disadvantage that all 

 objects for use with it 

 must either be selected 

 or specially mounted. It 

 has been described by the 

 designer at some length in 

 the seventh volume of the 

 ' Monthly Microscopical 

 Journal/ p. 237, in which 

 he states that by its use 

 the markings on A. pel- 

 lucida were brought out FlG 



by an eighth objective, 



which had never shown them before. Fig. 49 gives a 

 sectional . diagram of the illuminator, which has been 

 manipulated from Mr. Wenham's sketch. In using this 

 accessory, the glass cylinder is brought up level with the 

 stage, the centre of rotation is set truly by a dot on the 

 fitting, as seen with a low power. A drop of water is now 

 placed on the top of the cylinder, upon which the slide is 

 laid. The effect on the Podura scale is superb, the whole 

 surface appearing dotted with bright blue spots in a zigzag 

 direction. The plane mirror is the best for throwing up 

 the light, and when the finest effect has been obtained 



