PROCEEDINGS OF TUE SOCIETY. 105 



than it was fifty years ago, and they must aim at producing a stable 

 optical bar with all parts adjustable and removable. 



The question of resolving power was considered, and its relation to 

 the wave-length of the light. Limits of visibility were much extended 

 with a bright object against a darker ground, and the use of invisible 

 radiation of small wave-length, perhaps even soft X-rays, would extend 

 the limits of resolution. 



Mr. F. Martin Duncan, F.R.M.S., F.R.P.S., F.Z.S., President of 

 the Photomicrographic Society, gave a resume of his paper, "Some 

 Notes on the History and Design of Photomicrographic Apparatus," 

 drawing special attention to the following points : — 



The discovery of photography was due to British and French 

 scientists, and the first to apply successfully photography to the record- 

 ing of microscopic objects were Fox-Talbotin England (1835), Daguerre 

 in France, and Draper in America. Since that date all the important 

 advances and discoveries in photography had been made by scientific 

 workers in those three countries. He drew particular attention to the 

 admirable design of photomicrographic apparatus by British manufac- 

 turers in pre-war days, and to the superiority of the best British micro- 

 scope stand for accurate research work and photomicrography. 



Sir Herbert Jackson, K.B.E., F.R.S., emphasized the objects of 

 the Symposium, which were to consider methods of promoting the 

 science of microscopy, developing and improving the instruments, and 

 extending their use in science, industry and education. 



Beginning with the subject of glass, he said that while our makers 

 could equal the best obtained from abroad, new glasses were needed 

 with optical constants different from those at present known if new 

 and improved optical combinations were to be achieved. 



Mathematical investigations in the design of lenses and optical 

 systems were in progress, and they foreshadowed important develop- 

 ments, but much experimental work would be necessary. 



The growing use of the microscope in industry called for systematic 

 education in theory and practice. He drew attention to the new School 

 of Technical Optics at South Kensington, and pleaded for support and 

 encouragement. Lack of knowledge often led to wrong interpretation of 

 results and to the consequent neglect of the instrument. Training, such 

 as was given in spectroscopy, was essential, and he outlined the kind of 

 course he had in mind, an important feature of which was the study 

 of the use of the microscope under all conditions of illumination and 

 powers. 



Professor F. J. Cheshire, C.B.E., President of the Optical Society, 

 followed with a paper on "The Mechanical Design of Microscopes." 



He showed how the microscope was the keystone of the arch of a 

 key industry, and therefore its manufacture must be in a healthy and 

 thriving condition. To efiFect this " mass production " must follow the 

 stage of " artistic production," depending on extraordinary personal 

 skill. It must meet the demands of the manufacturer as well as of the 

 user, and therefore be made cheaply as well as accurately. This called 



