96 PRACTICAL PHOTOMICROGRAPHY. 



the dark parts of the negative ; the whole plate should look as 

 if it would be a very great deal too dark but for the fixing 

 operation. J3ut it must by no means be opaque nor equally 

 dark all over, nor must there be any part where the shape of 

 the flame is clearly visible, as through clear glass. Looking at 

 the face (film) of the plate, some parts should seem quite 

 black, others dark-gray, others (the shadows) paler gray but 

 not white. Practice alone, and as before consideration of the 

 various qualities of various subjects, can ever teach us what is 

 perhaps our most difficult lesson next to proper exposure, viz. : 

 when to stop development. 



In cases of error in exposure, if the error is but slight we 

 can almost always make our negative as good as if we had ex- 

 posed correctly. And further, there are certain subjects which 

 cannot by exposure alone without a little " dodging " in after 

 processes be rendered to the best advantage. We have sug- 

 gested a method of treatment for subjects presenting violent 

 contrasts. We presently shall touch on other abnormal sub- 

 jects. 



But we must now mention another system of development 

 which has marked advantages for the beginner ; its chief dis- 

 advantage being that in using it we have not the same useful 

 guides to judgment of exposure. This system is usually called 

 slow development, and as a rule the carbonates are the alkalis 

 used. The difference consists simply in starting development 

 with a very weak developing solution, and adding the reagents 

 if necessary little by little till the full normal dose is reached 

 or the full effect produced. Thus we may start with pyro, 2 

 grains ; bromide, 1 grain ; ammonia, 1 minim ; and, after 

 (say) 3 minutes add a minim more of ammonia, and so on for 

 a space of from 20 minutes upwards, or we may start with 

 only 5 or 6 grains of the combined carbonates and pursue a 

 similar course. The writer has never in ordinary photography 

 found the slightest benefit to arise from such a prolongation 

 of development, unless it be that in certain cases more contrast 

 of light and shade is obtained by the slow method. The tyro 

 has perhaps more time to make up his mind when to stop de- 

 velopment, but in the system recommended by us he has cer- 



