38 



PRACTICAL PHOTOMICROGRAPHY. 



Nor does the writer commit himself to any opinion as to the 

 merits of a contrivance known as an "Amplifier," and con- 

 sisting of an achromatic concavo-convex or double-concave lens 

 inserted behind the object glass ; he has not himself tried such 

 an arrangement, but has seen specimens of work produced 

 with its aid which do not seem to speak highly in its favor, 

 though per contra he has seen very creditable work produced 

 in its presence. 



FIG. 9. BULLS'S-EYE ON STAND. 



The bull's-eye does not require special mention in this 

 chapter; it is usually a plano-convex glass used with its plane 

 surface next to the radiant, and the larger it is, without being 

 clumsy, the better, though by some a small bull's-eye is pre- 

 ferred. A small bull's-eye, having a shorter focus, gives more 

 brilliant illumination than a large one. 



