42 THE PRESENT POSITION AND THE FUTURE. 



defined if they exceed the resolution limits as laid down for recur- 

 ring structures. It cannot be too fully appreciated that illum- 

 ination is the keynote of all sound microscopic work, and this applies 

 whether the illumination is by means of visible radiation under 

 ordinary conditions of w^ork, or whether it is in experimental work 

 in which the use of invisible radiations are concerned. 



There is much room for research in this direction, and it is to 

 be hoped that this is one of the points which will be seriously taken 

 up. Apart from any question of research, the education of the 

 user is perhaps of vital importance. It is little use for opticians 

 to make great efforts to turn out a satisfactory instrument if the 

 user is incapable of taking advantage of the quality of the optical 

 or other parts. I trust, therefore, that this Symposium will give 

 an impetus in this direction, and that it will help microscope users 

 to realise how much remains to be done. 



