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SUMMARY OF CURREN-r RESEARCHES RELATING TO 



illumination the distance of the eye-piece from the field or condenser 

 lens must be adjusted so that its Ramsden circle and the other objec- 

 tive in the camera are in conjugate foci with respect to the field lens. 

 The Microscope can be used with any Microscope objective. It is found 

 convenient to place the exposure shutter and compensating filter at the 

 end of the tube just behind the Microscope eye -piece, although other 

 equally good positions might he found for these. So far as photo- 

 micrography is concerned, it is evident that the prismatic dispersion 

 method, in common with all screen-plate methods of colour photography, 

 is not suitable for work which requires the finest definition of individual 

 elements. Its utility applies chiefly to stained objects, or to objects 

 illuminated by Rheinberg's colour illumination : in short, to objects 



Fig. 85. — Camera as used in conjunction with the Microscope. 



where colour differentiation forms one of the main features. It should 

 also afford a striking means of reproducing polarized light effects. The 

 authors state that that is all that can be said as yet with regard to 

 photomicrography, a sufficient range of experiments in that direction not 

 having yet been made. 



Making of Photomicrographs.* — J. Cockburn writes in refer- 

 ence to the failure of prints as regards clearness and definition, and 

 gives his own procedure : — " Get, of course, as sharp a focus as possible, 

 using a magnifier of low power on the focusing screen, and do not on 

 any account try to get a large-sized negative at once. Using a rather 

 slow plate, with as little grain as possible, and presuming that an eye- 

 piece is used on the Microscope, get the plate at such a distance from 

 the eyepiece that the resulting negative will be 1 in. or 1'5 in. in 

 diameter. After developing and fixing this, and seeing that it is free 

 from fog, take a contact transparency (positive) from it, either on a fine 

 make of lantern plate or with transparency carbon tissue. From this 

 positive make a negative by means of a lantern to a diameter of double 

 * Brit. Med. Journ. (1912) i. p. 704. 



