THE MICROSCOPES OF 1894. 



331 



is also a slot, cut at the angle of 45^, for the insertion of the quartz 

 wedge. The polariser is pivoted to swing in and out of the field ; 

 it has a circle divided into eight and clicked at o^ and 180^ to 

 indicate where the nicols are crossed. The eyepiece is furnished 

 with crossed webs. 



Fig. 8. 



