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On a New Stage Arrangement for the Examination of 

 Objects by Reflected or Transmitted Light. 



By N. E. Green, F.R.A.S. 

 (Bead February 25th, 1876 j. 



This stage arrangement may be described in very few words. It 

 consists of a plate of brass, 3in. by 2, which lies on the stage of the 

 microscope. It has a large central bole to admit of free action in 

 the condenser attached to the sub-stage. At the upper and lower 

 sides of this hole there are two pieces of brass attached to the 

 plate, about f of an inch in height, having two springs on their 

 upper surfaces for holding the slide, which is thus placed in a 

 direction at right angles with the usual position ; a condenser of 

 short focus is placed at the side, and throws on the object an 

 intense spot of light from a Silber burner. This arrangement, 

 though exceedingly simple in itself, has resulted (and that almost 

 unexpectedly) in a great increase of power. The old plan had 

 been to produce the necessary elevation above the stage of the 

 microscope by means of a mahogany block, which only permitted 

 the passage of an exceedingly thin wedge of light ; just as much as 

 could be forced between the object glass and the object. By the 

 new arrangement not only is this secured, but all the lower half of 

 the condenser comes into use, throwing up its light from below 

 the slide, and yet in such an oblique direction that it does not 

 enter the object glass ; so that dark background is possible up to 

 a ^g. As a final result it may be stated that this illumination, 

 is in many respects equal, and in some superior, to that previously 

 obtained by the lime light. 



With regard to the employment of transmitted light from the 

 reflector, tbe large hole in the brass plate permits the freest 

 action about the achromatic condenser, which is passed forward 

 by the rackwork of the substage, till it nearly touphes the under 

 portion of the slide. It is then possible to arrange both lights on 



