350 THE president's address. 



back of the horse-slioe ; this constitutes an ingenious and novel 

 feature. 



During the past twenty years a change for the better can be 

 noticed in the box of apparatus. It has got smaller and smaller 

 until it has entirely disappeared. Perhaps a little too much has 

 been improved away. For instance, for opaque objects there 

 has been no illuminator invented that will compare with the 

 lieberkiihn; a complete outfit, therefore, should have lieberkiihns 

 with all powers from two inches to a half inch. Of course, it will 

 be said that a side reflector serves all the purposes of a lieber- 

 kiilm, and that one piece of apparatus is better than several. 

 It is very true that a side reflector can be used with the lower 

 powers, but hardly with a half-inch, unless its aperture be 

 ver}'' low ; besides this, the question of all round illumination as 

 against that on one side only is opened up. 



With this improvement in the box of apparatus it is to be 

 feared that one little thing has been forgotten, viz., that a single 

 substage condenser is insufficient for all kinds of work. Two 

 are necessary, one for high powers, which should itself be at least 

 of quarter-inch power and wide in angle, the other a low power, 

 more moderate in angle, with stops, etc., for dark ground illu- 

 mination ; the upper lens of this condenser should be I'emovable, 

 so that the lower lenses may be used for very low power work. 



The substitute for these two condensers is found in a wide 

 angled low power condenser, which is too low in power, and too 

 full of spherical aberration, for high power work, too high in 

 power for low power work, and which really is only suitable for 

 objectives of medium power, such as half -inch to quarter-inch. 

 It reminds me of a pocket bath that was advertised some years 

 ago, wdiich was bad for the pocket and useless as a bath. So 

 also a single condenser is good neither for high nor for low 

 power work. 



It is to be feared that a serious danger is likely to occur to the 

 *' microscopy " of the future, owing to the neglect of viewing 

 opaque objects with a stereoscopic binocular. Personally, I do 

 not believe that any observer, however eminent, who has not 

 previously passed through the special training of viewing opaque 

 objects with a stereoscopic binocular, can form correct ideas of 

 the shape of objects solely by alterations of focus. This is such 

 an important subject that the necessity for some such training 



