THE AMERICAN 



MONTHLY 



MICROSCOPICAL JOURNAL 



VOL. XVIII. APRIL, 1896. No. 4. 



The Development of Photomicrographic Negatives, 



Bv Dr. W. C. BORDEN, U. S. ARMY. 



Fellow of the Royal Microscopical Societ3-. 



[with frontispiece.] 



The development of the exposed plate is one of the 

 most important steps in the photomicrogTaphic process. 

 However well the illnmination may be arranged and how- 

 ever carefully the adjustments and exposure may have 

 been made, the process will fail of successful or perfect 

 result, l>y poor, or imperfect development of the latent 

 image. 



In almost all photomicrographic work contrast has to 

 be sought for and next after detail and sharpness, or 

 rather in conjunction with them, contrast is necessary in 

 the negative to give a print having the requisite clear- 

 ness. 



To obtain detail a proper objective must be combined with 

 suitable substage illumination. The light must be accurate- 

 ly focussed on the object by the substage condenser and the 

 aperture of the latter must bear proper relation to the 

 aperture of the objective. With detail obtained, sharp- 

 ness is had by not extending the angle of light from the 

 substage condenser beyond a degree necessary to show 

 the detail and by accurately focussing the image on the 

 camera screen. 



In addition, a suitable plate must be used, and, if nee- 



