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On a Simple Means of Illuminating Objects with Low 

 Powers by Artificial Light. 



By G-. C. Karop, M.R.C.S., F.R.M.S. 

 (Bead May loth, 1896J. 



Some little time back I was asked the best way to examine 

 microscopical specimens, requiring only low powers, by artificial 

 illumination. What exactly the best way may be is, of course, 

 a matter of opinion ; but judging from the very inefficient, not 

 to say bad manner in which such objects frequently are 

 exhibited, even at this Club, it might be profitable if I were 

 permitted to describe a simple means of obtaining a pleasant 

 equably lighted field with sufficient intensity and of such a tone 

 as to permit of a prolonged examination of low power specimens 

 without fatigue. 



Such an illumination was felt to be a desideratum in quite 

 early microscopical days, and in all the older text-books will be 

 found descriptions of apparatus to serve this end, ranging from 

 simple contrivances like waxed paper, ground glass and plaster- 

 of-Paris mirrors to light modifiers, reflector screens, white-cloud 

 condensers, double parabolic specula, and many more elaborate 

 devices. It is pretty obvious, therefore, that nothing very new 

 or striking is likely to be invented for the purpose now, when 

 the tendency is to diminish rather than multiply apparatus ; so 

 without any pretence of novelty I will merely describe the 

 simple affair I myself have found very useful, and this will 

 probably be the means of educing other, and perhaps better 

 methods, from those who have felt the same want and have 

 encompassed it in other ways. 



The idea is firstly to intensify the light and then spread it 

 over a large surface. For the intensification I use the lower, 

 crossed lens of the Abbe condenser, but any suitable fairly large 

 lens of about one inch focus will do as well, either a double 

 convex or the field lens of an eye-piece. This is screwed into 



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