ZOOLOGY AND BOTANY^ MICEOSCOPY, ETC. 



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piece so that it is not disturbed by the centering of the stage, and at / is a 

 small aperture through which the observer reads the scale from a vertical 

 position by means of the inclined mirror shown in fig. 37. The rotation of 

 the upper part of the Microscope is confined within very narrow limits by 



Fig. 



the two screws r r of fig. 37, and is only employed to bring the index and 

 zero point of the scale into coincidence after centering. The cover li and 

 circular band g serve as protections for this part of the instrument. 



