1896.] MICHOSCOPICAL JOURNAL. 115 



No. 2. Sodium Carbonate 15 grammes. 



Water 250 c. c. 



Use e(inal parts of No. 1 and No. 2. 



Development should proceed slowly and gradually and 

 should he continued until suflBcient density is obtained. 

 Frequently all the detail appears while the plate is still 

 quite thin and the novice i.s apt to fear a flat plate and 

 remove it from the developer before development is com- 

 pleted. This is to be avoided, for density is necessary, 

 and if after it is obtained the fixed plate has the parts 

 clogged which should be clear, the exposure has been too 

 long and another should be made. A thin plate, in pho- 

 tomicrography, after prolonged development generally 

 means under exposure even if all details are present. 



The image should not appear too quickly after the de- 

 veloper has been applied. Frequently with objects of 

 little contrast the exposure has to be shortened as much 

 as possible in order that contrast may be obtained, and in 

 such cases, the image may not appear for a minute or 

 two and development may have to be prolonged for fif- 

 teen or twenty minutes. A small box with a easily re- 

 movable cover which will exclude all light should always 

 be at hand on the developing table. In this the develop- 

 ing tray may be placed and left for some time in case of 

 slow development. This allows the operator to leave the 

 developing room and proceed with other work, or make 

 another exposure, while development is going on. A 

 cardboard or other cover for the developing tray should 

 be at hand to place over the tray during the development 

 of orthochromatic plates for they are somewhat sensitive 

 to ruby light and should be guarded from it as much as 

 possible during development. It is best to place them in 

 the tray and flow the developer over them at some dis- 

 tance from the light, then cover them and not examine 

 or expose them to the light longer, or more frequently, 

 then necessary. 



