PKOCEEDINGS OF THE SOCIETY. 107 



The author is of opinion that advances in numerical aperture offer 

 little attraction. Abbe carried the N. A. too far, and no notable discovery 

 had been achieved with his monobromide-immersion objectives of N.A. 

 1*60. The rise in ultra-violet light was more promising, but the 

 technical difficulties and limitations were great. 



Dr. R. MuLLiNEUX Walmsley, Chairman of the Technical Optics 

 Committee of the British Science Guild, outlined the work of that 

 Committee. 



The first step taken was the Conference held in 1915, as a result 

 of which three specifications were drawn up, one for a pathological 

 microscope, another for a student's, and a third for a metallurgical 

 microscope. These specifications were published in 1916, and amended 

 specifications are now about to be issued. 



Mr. Conrad Beck, C.B.E., F.R.M.S., read a paper describing "A 

 Standard Microscope," which his firm was making, to fulfil the require- 

 ments of the British Science Guild Specification. 



The form and dimensions of the microscope are described in detail 

 in the paper. The novel features include the fine adjustment, a new 

 object glass changer possessing many advantages over a revolving nose- 

 piece, and a new micrometer eyepiece and system of measurement. 



A supplementary paper emphasized the necessity for research on 

 the use of the microscope. The search for an illuminator by which 

 much larger angles could be used in the object glass, and a method of 

 illumination which would modify the diffraction-images, seen for 

 example when micro-organisms were examined by dark-ground illumina- 

 tion, were cited as instances of such researches. Other examples were 

 the relation between resolution and the increase of brilliancy induced 

 by wide apertures in the condenser, and in metallurgical work a means 

 of illumination to eliminate flaw and ghost images. 



Mr. F. Watson Baker, F.R.M.S., spoke on " Progress in Micro- 

 scopy from a Manufacturer's Point of View." 



So long as thirty- eight years ago microscopes were made in this 

 country which anticipated the requirements of to-day, and when apochro- 

 matic objectives were first introduced the only microscope which allowed 

 of the full advantage being taken of the optical qualities was the British 

 instrument. British makers had always excelled in the making of 

 microscopes of high class, involving skilled hand work. 



The hand-workers of the past had, however, become reduced by 

 dispersion and death, and partly on this account, and in order to reduce 

 the present heavy costs, steps had been taken to produce microscopes 

 by means of machine tools, and such instruments would be available 

 in the near future. 



Mr. Powell Swift read a paper on "A New Research Microscope," 

 which described a model shown embodying the results of consultations 

 held between makers and users. 



