160 Notes. 



involves so much false colour and spurious detail as to be of no 

 practical value. The real merit of a post-objective stop is to 

 give accentuated value to the widely-refracted light on the principle 

 explained in Toppler's paper, and its practical value in this way 

 can hardly be overstated. But the only practicable position in 

 which to mount it is just above the eye-lens in the Ramsden disk. 



