METHODS OF RESEARCH: APPARATUS 95 



whether an ordinary plate or an orthochromatic plate will give 

 best results, colors having much the same appeal to the eye 

 sometimes behaving differently on the dry plate. The writer 

 uses Seed's rapid, gilt-edge (non-isochromatic) plates for some 

 purposes and for others Cramer's instantaneous and slow iso- 

 chromatic plates, also Hammer's non-halation (double coated) 

 orthochromatic plates, and for exact color values Wratten and 

 Wain wright's Process Panchromatic plates, these last being very 

 sensitive even to dull red light. 



Any one of half a dozen developers may be used. It is good 

 to stick to one until you have mastered it. We use at present 

 Citol which has the advantage of great simplicity, the only 

 preliminary to its use being its dilution with 20 parts of distilled 

 water, more or less, according as the plate is under or over 

 exposed. For contrasts in photomicrography I use a hydro- 

 chinon developer. 



Washing Devices. Two washing tanks made by Burke and 

 James, (Jackson Blvd. and Desplaines St., Chicago, 111.), have 

 proved very useful. The one for negatives takes any size 

 without readjustment, and jets currents of water over the nega- 

 tives from two directions, thus insuring a very thorough circu- 

 lation and removal of the fixative in a minimum time. The one 

 for washing prints also has an ingenious device for keeping the 

 water in circulation and the prints separated and moving about. 

 They should be made of tinned copper, but unless specially so 

 ordered they are made of galvanized sheet iron which soon rusts 

 out. 



The Developing or Dark-room. The dark-room should be 

 impervious to light. If it is set up in part of a larger room 

 after the construction of the building, the walls may be of inch 

 pine boards, matched, and should be covered inside with heavy 

 carton (composition) board which must be painted a dead (lus- 

 terless) black. 



By preference, the entrance should be through a labyrinth 

 (a reversed and flattened letter S, or if one thinks of the walls 

 rather than of the passage way, then two linked letter U's (p) 

 opening outward into the darker part of an ante-room. Doors 

 are inconvenient, and if they open directly into the dark-room 



