CH. ff\ 



LA BORA TOR Y MICROSCOPES. 



65 



Fig. 67. A'ranss' Method of Mark- 

 ing Objectives, on a Revolving Nose- 

 P. ece. 



As seen in the figure, the equiva- 

 lent focus of the objective is engraved 

 on the diaphragm above the back lens 

 and may be very readily seen in ro- 

 ta I iug then ose-p iece. Th is is of great 

 advantage and facilitates the chang- 

 ing of objectives, as one can see what 

 objective is coming into place with- 

 out trouble. 



Figs. 6S-69. The Tolles-Mayall Mechanical Stage (j 



Both these mechanical stages have the great advantage of large movement in both 

 directions, so that a series may be studied with great certainty and facility, Both have 

 scales and verniers, so that the position of any particular feature of a preparation may 

 be readily re found The figures on the scale being different there is never doubt as to 

 the position of each from the record. 



Fig. 68. The Tolles Mayall mechanical stage as constructed by Leitz. It is shown in 

 position 011 the stage of the microscope : it is fastened to the stage by a pin and screw 

 near the pillar. 



Fig. 69. The Tolles Mayall mechanical stage made by the Bausch & Lomb Optical 

 Company. It is separated from the microscope. It is attached to the microscope by a 

 clamp surrounding the pillar. This form of connection was employed by Reichert & 

 Zeiss in the earlier forms devised, and is still used by them 



