94 



corresponding magnification = 12 diameters - - or a suitable compensating eye- 

 piece and a very carefully constructed micrometer with divided drum. The 

 glass plate, with a crossed as well as a double line, is moved across the field 

 by means of the micrometer screw. Each interval of the divided drum corre- 

 sponds to a movement of 0.01 mm of the point marked. Complete revolutions 

 of the drum are counted by means of a numbered scale seen in the field. The 

 measurement can be extended over a tract of 4 mm of the objective image. 



The absolute values corresponding to the divisions of the drum should be 

 determined by the aid of a stage-micrometer for each separate objective. 



Price : Code-words : 

 No. 124 : Screw Micrometer Eye-piece for achromatic objectives, 



in case Marks go. . Peal. 



,, 125: Screw Micrometer Eye-piece with compensating eye- 

 piece 6, in case , . . ,, 705. . Pebetero. 



For the exact measurement of objects too large for inclusion in one visual 

 field of the microscope we construct the * Stage Screw Micrometer, No. 126 

 (see Fig. 53). A slider moved by the micrometer screw carries a rotating disk 

 with divided circle. The divisions of the drum indicate 0.002 mm; complete 



Fig. 53. Stage Screw Micrometer, No. 126. 



(Vs Full Size.) 



