At the conclusion of his paper Mr. Conrad Beck spoke 



on " Research in the Use of the Microscope." 



RESEARCH IN THE USE OF THE MICROSCOPE. 

 By Conrad Beck. 



In a series of lectures on the Theory of the Microscope which I 

 delivered at the Society of Arts in the years 1907-8, 1 concluded 

 with some remarks on the necessity for research on the use of the 

 microscope. The methods upon which we now rely for the finest 

 results obtained with high powers and for the best methods of 

 illumination obtained with low and moderate powers are chiefly due to 

 the work in the past of British amateur microscopists who have 

 worked at the subject as a hobby and not as a profession. Now 

 that the simpler problems have been solved, further improvements can 

 only be looked for as the result of a combination of theory and 

 practice which we can scarcely expect from any but trained research 

 workers who can bring to the subject a combination of high optical 

 knowledge and great skill in manipulation. Such work will, no 

 doubt, require the co-operation of the manufacturer, but it is 

 hopeless to expect that the manufacturer himself w^ll have time to 

 devote to the elucidation of the problems themselves. At the present 

 time there are a large number of questions which will have to be 

 solved before any very considerable progress is made in the science 

 of microscopy. 



In the lectures to which I refer I indicated, as an example of 

 a possible direction for study, the ingenious suggestion of Mr. J. W. 

 Gordon for reducing the size of the diffraction disc by the use of 

 annular beams of light. This was only one point to illustrate the 

 need of microscopical research. It is well understood that high 

 power resolution depends on the aperture of the object glass, and 

 yet in the new and extremely promising field of work opened up 

 by dark ground illumination, we are deliberately reducing the aper- 

 ture of our object glass to .9 or even .7 numerical aperture. There 

 is no essential reason why an illuminator could not be devised by 

 which much larger angles could be used in the object glass. 



In the study of bacteria by dark ground illumination the 

 diffraction images caused by the micro-organisms are extremely con- 

 fusing, and there is room for research as to whether these images 

 could not be profoundly modified by different methods of illumina- 

 tion, and to what extent the diffraction images indicate the struc- 

 ture of the organisms. 



Another question, which, in my opinion, calls for serious 

 research, is whether and to what extent a wide angle cone of light 

 used in examining a histological specimen reveals or diseuises struc- 

 ture, and to what extent the increase in brilliancy of ilhmiination 

 induced by opening up the aperture of the condenser increases or 

 reduces the perfection of the image. I do not think there has been 

 a satisfactory investigation on the examination of this class of 



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