108 PROCEEDINGS OF THE SOCIETY. 



The special points considered are rigidity ; diameter of body, which 

 is 2 inches, enabling a photographic lens placed in its interior to cover 

 a large field ; and the novel construction of the substage, which is of 

 great advantage for physical research, as it enables special apparatus 

 to be introduced and produce, as occasion may require, a most perfect 

 optical bench for general experimental work. There is a considerable 

 class of delicate optical research which calls for an optical bench possess- 

 ing the perfect adjustments of a microscope, and hitherto this require- 

 ment has not been met. Almost any class of apparatus could be applied 

 to the stand for making small and accurate measurements in physics, 

 and although the chief object of this instrument is to provide the most 

 perfect microscope that can be required, the other function for such an 

 instrument has been borne in mind. 



The Chairman having invited discussion on the three papers first 

 presented : — 



Mr. J. E. Barnard announced that at the suggestion of some of 

 the makers a small standing committee would be appointed, consisting 

 of the Presidents of the Societies meeting that evening and one or two 

 others, to test the apochromatic objectives now being manufactured by 

 English firms. 



Dr. R. MuLLiNEUX Walmsley said that to enable microscopes to 

 be successfully produced in large quantities called for thoroughly trained 

 men in the inspection room of the factory. The educational aspect was 

 therefore all-important. 



Lieut.-Col. GiFFORD criticised existing apochromatic objectives on 

 the ground that they were mostly not truly apochromatic. 



Instructor-Commander Ainslie spoke on apochromatic objectives 

 from the point of view of resolution. While the best English lenses he 

 had used were of superlative excellence, he urged the necessity for a far 

 higher average of excellence than was the case at present. 



Dr. E. C. BousFiELD also spoke on apochromatic lenses and the 

 conditions required for making them perfect and lasting. A fault 

 difficult to obviate was roundness of field. He described a better 

 distance focusing arrangement for photomicrograph ic work than that 

 usually employed. 



Dr. W. RosENHALN, F.R.S., pointed out that it was important to 

 distinguish between mass production of a standard microscope and the 

 progress of the microscope as an instrument of research and precision. 



Mr. Arthur Banfield, in a written communication, suggested 

 possible improvements in the microscope as a result of his experience. 



The following papers were presented and taken as read : — 



" Notes on the Future of the Microscope," by M. Eugene Schneider. 



{a) Mechanical Improvements. — A universal screw is suggested for 

 the tubes in which eyepieces and condensers slide. 



{h) Optical Improvements. — We are restricted, at least in usual 

 practice, by the impossibility of going beyond the numerical aperture 

 of 1-40. Better correction of the aberrations and especially of the field 



