j Q __^__ 



The exceptionally low power ocular 2, known as the Searcher Ocular, 

 serves to extend the effectiveness of the various magnifications required to be 

 successively used with any one objective as far as possible downwards through 

 the lower strata of a specimen, also to facilitate preliminary examination 

 and the process of searching for particular points of the object when high- 

 power objectives are being used. 



The Working Oculars vary in magnifying power from 4 upwards, and even 

 their highest powers can be used with the greatest comfort. In all of them the 

 eye-point (the exit pupil) lies sufficiently high above the upper lens surface, 

 and the diameter of the lenses is sufficiently large, to completely obviate the in- 

 conveniences formerly attending the use of oculars of short focus. 



We have modified one of the series of compensating ocu- 

 lars - the X -I ~ ' fitting it with a collective lens of large 

 diameter. Under this modification it is designated Compensa- 

 ting Ocular 4*. As compared with the ordinary Compensa- 

 ting Ocular 4, its field is considerably enlarged. To 

 use this ocular with Stand |, the ocular-tube is unscrewed out 

 of the draw-tube -- with Stands III and IV the draw-tube is un- 

 screwed at the shoulder and the Compensating Ocular 4* screwed 

 in instead. It is fitted with a revolving collar and can be fixed 

 rigidly in any desired position by means of a clamping screw K. 

 An iris-diaphragm, by means of which the area of the 

 field may be varied at will - - frequently a great convenience 

 in demonstrations -- takes the place of the ordinary fixed dia- 

 phragm. The eye-lens is mounted in a sliding sleeve, after the 

 manner of our micrometer oculars thereby adapting it for use 

 with a scale, &c., when desired. 



Fiir. 5. 



Ompensatiiifr Ocular 4* 

 with iris-diaphragm. 



('/., Full Size.) 



The enlargement of the area of the visual field is, however, of real practical value 

 only in the case of the lower-power objectives of 16 mm and 8 mm, because the sharp field 

 of the higher powers is not sufficiently large to satisfactorily fill the field of this ocular. 



Should this special ocular be employed on a Stand III or \\l, possessing neither Nose-piece 

 or Sliding Objective- Changer, an intennediate adapting ring of definite length must be sc reived 

 into the main tube. 



Regarding the use of this ocular with a special form of ABBE'S drawing apparatus 

 see p. 73. 



n_ 



JI! 



