PHOTO MICROGRAPHY 



INTRODUCTION 



By Photo-micrography is meant the art of photographing a magnified image. Seeing 

 this impHes reproduction of images of any ampHfication, so for convenience of 

 description we may divide the subject into three heads : 



1. Low- Power Work : — Treating with magnitudes from i|- to about lo 

 diameters ; 



2. Medium -Power Work, which deals from lo to about 600 diameters ; and 



3. High-Power or Critical Work, which, commencing where moderate 

 ends, reaches to about 3000 diameters. 



It would seem as if there existed in this arrangement a very unequal division of 

 the subject, especially that low power work should not extend beyond 10 diameters; 

 but it must be at once stated that up to this limit photo-micrography is quite a 

 different matter, and indeed requires in point of fact an entirely different form of 

 apparatus. We should, however, recommend those commencing to begin from the 

 very commencement, inasmuch as the difficulties presented become greater and greater 

 as the initial magnification increases. 



Inasmuch as an artificial light is always required for all the three divisions of our 

 subject, we shall first discuss illuminants in general. 



A 



