PRACTICAL PHOTOMICROGRAPHY. 97 



tainly 3 minutes, probably 4 or 5, to examine progress, and he 

 can hardly want more ; further, by the slow process 15 or 20 

 minutes will be needed simply perhaps to find out that another 

 exposure is required. Those, however, who lean towards slow 

 development may refer to any of the Scovill series of photog- 

 raphic books, where they will find full details. 



ABNORMAL DEVELOPMENT. 



It has been said that if the error in exposure has been but 

 trifling a perfect negative may still be made. It is better in 

 most cases to make a fresh exposure, but this proceeding may 

 not at all times suit the worker, and further it is well to gain 

 a little mastery over, and tact in, manipulation of the developer. 



If appearances cited above show that the plate has certainly 

 been underexposed, the developer should at once be thrown 

 away and the plate washed. Thereafter a fresh developer is 

 applied containing less pyro and bromide. Thus : Pyro 1 to 

 1J grains. Bromide -| a grain. Ammonia as before. Or 

 water may be added to the first developer which is to be im- 

 mediately reinforced with alkali. If the plate is known before 

 development to be underexposed to a considerable extent, it 

 may be soaked in the alkali and water of the developer alone 

 for a couple of minutes, the pyro and a modified quantity of 

 bromide to be added thereafter. But an underexposed plate 

 as a rule is useless, no matter what we do with it. 



With overexposure the matter is different, for a plate grossly 

 overexposed can be saved if it is taken in time. The difficulty 

 is to catch it in time and to apply the cure in time. Bromide 

 certainly restrains detail but unfortunately it also keeps back 

 density, and in a severely overexposed plate density of the high 

 lights is the very thing most lacking. If the overexposure be 

 only enough to make the plate very Hack all over, or as is the 

 usual case, very black and dark grey, the simplest cure is to 

 add water to the developer and to stop development earlier 

 than if the plate were properly exposed. But if the overex- 

 posure has been sufficient to make the image grey all over, the 

 best plan is to watch carefully till every detail seems out and 

 then instantly to flood the plate with water containing, for 



