MICROSCOPE AND CAMERA ALLIED 



which quite satisfactory photo-micrographs may be 

 taken. It consists of a light metal cone, the more 

 pointed end fits over the upper portion of the 

 microscope tube; the other end of the cone is 

 provided with ground and plain glass focussing 

 screens and a dark slide. When using this appara- 

 tus, it is first necessary to find and focus our object 

 in the ordinary way, before attaching the photo- 

 graphic apparatus. Having secured our object 

 exactly as we wish it to be depicted and well in 

 the centre of the illuminated circle, we remove the 

 eyepiece and slip the metal camera over the top 

 of the microscope tube. If now we place the ground 

 glass screen in position, we can see an image of our 

 object upon it. Great attention must be paid to 

 the lighting, it is necessary that the illumination 

 be perfectly even, otherwise our negative will be 

 over-exposed in some parts and under-exposed in 

 others. When everything is in order the plain glass 

 screen is substituted for the one of ground glass. 

 On this we shall probably not see any image with 

 the naked eye, but with the help of a magnifying 

 glass we can see a much finer image than was pos- 

 sible on the ground glass screen. The final focus- 

 sing is done at this stage and, having secured as 

 sharp an image as possible, the focussing screen is 

 removed and the exposure is made. Experience 

 alone will teach the length of exposure, it depends 

 upon the amount and nature of the light, upon the 

 transparency of the object and also upon its colour. 

 There is no more simple apparatus for taking 



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