ELEMENTARY PHOTO-MICROGRAPHY. 



33 



should study the use of the bull's-eye, as described 

 in the next chapter. This will save repetition here, 

 and probably the mistake too often made by be- 

 ginners in supposing a powerful light to be all 

 sufficient for getting a good negative. 



On the contrary, it is not so much the brilliancy 

 of the illumination as its right application that 

 makes it effective. 



Even a common nightlight in the hands of an 

 expert might yield better results than acetylene 

 gas at the service of a novice. 



The camera, specimen-holder, and lamp should 

 now be as shown in fig. 9, with all centres in 

 one line. 



FIG. 9. 



C, Camera. S, Specimen. G G, Ground-glass. B, Bull's-eye. 

 L, Lamp. 



Having focussed the object sharply by means 

 of a focussing glass the naked eye being quite 

 unable to discern the point of best definition and 

 interposed a piece of ground-glass between lamp 

 and object to distribute the light and give even 



