SOME SPECIAL PEOCESSES 



253 



TABLE V 



MAGNIFICATIONS AND OPTICAL CAMERA-LENGTHS 



For the Monochromats and the Quartz Eye-pieces at 160 mm. 

 Tube-length and X = 275 /ut. 



The effective N.A. is doubled in each case owing to the wave-length 

 of the light used. 



is immersed must be one that does not offer any obstruction to 

 the passage of ultra-violet light. The whole process is not a 

 simple one, and it must be admitted that at first the results 

 may not prove so satisfactory as might be anticipated. It is 

 essentially one that calls for the exercise of considerable patience 

 and not a little skill. But once the manipulation has been 



