24 PHOTO-MICROGKAPHY 



must be pushed up to the object to be photographed, or away from it, according to 

 whether it required enlarging more or less. Those who have ever made any attempt 

 at trying this, the most primitive form of photo-micrography, will have already found 

 such apparently simple movement of the camera is often a very troublesome matter. 

 After having put the specimen in the centre of the ground glass, and made the light 

 uniformly even over the whole field, they may have proceeded, as it was pointed out 

 they should never neglect to do, to measure the image, and note by comparison with 

 the object the amount of magnification they were obtaining. Perhaps they then 

 found the image too large or too small. It seems now only a simple matter to shift the 

 camera forwards or backwards, but, as a matter of fact, they most likely found it a 

 very troublesome operation because, unless it was shifted exactly in the same axis, all 



Fig. II 



Fig. 12 





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the centreing of the light and the placing of the object into the middle of the plate, 

 had to be done over and over again until the magnification was exactly what was 

 wanted. We recognised this trouble when commencing the work some years ago, 

 and then devised a simple form of arrangement which was so cheap and effective that 

 we feel it may be of service to others to describe it somewhat fully. In Fig. 1 1 is 

 shown the camera — roughly depicted, but clear enough for the purpose — thoroughly 

 extended to about 12 or 13 inches, the base-board of the camera being seen at A, and 

 the focusing screen at F. 



The dotted lines through the base-board indicate where the ordinary screw hole is 

 placed, by which in the field the camera is attached to the tripod. Below the camera 

 in the drawing is seen another board marked 2 ; it is large enough to hold the camera, 

 the face of which fits well against the metal end marked "Brass" in the diagram. 

 Three holes are seen in it (the board), the centre one to take the ordinary tripod 

 head screw (shown in its place in the base-board of the camera) which fastens the 



