CH. VII] 



SLIDES AND COVER-GLASSES 



165 



Fig. 133. Cover-Glass Measurer {Edward Bausch). 



The cover glass is placed in the notch between the two screws, and the drum is 

 turned by the milled head at the right till the cover is in contact with the screws. 

 The thickness is then indicated by the knife edge on the drum and may be read off 

 directly in 0.001 of a millimeter or inch. In other columns is given the proper 

 tube-length for various unadjustable objectives (J, \, \, and ^ in.) {Bausch and 

 Lomb Optical Company). 



Fig. 134. Zeiss Cover-Glass 

 Measurer. With this the knife edge 

 jaws are opened by means of a lever 

 and the cover inserted. The thick- 

 ness may then be read off on the face 

 as the pointer indicates the thick- 

 ness in hundredths millimeter in 

 the outer circle and in thousandths 

 inch on the inner circle. 



\ 242. Cleaning Mixtures for Glass. — The cleaning mixtures used for clean- 

 ing slides and cover-glasses are those commonly used in chemical laboratories : 

 (Dr. G. C. Caldwell's Laboratory Guide in Chemistry). 



