. Carnegie Institution of Washington publication. VENTILATION OF DARK-ROOM. 149 LOADING SHELF 2 ft. 3 in. 5! DOOR I Fig. 135.* in use much of the time, some The writer accomplishes this by an electric fan placed in the mouth of an air-shaft which extends from the ceiling to 6 or 8 feet above the roof. These shafts are cylindrical, i foot in diameter, made of heavy sheet- iron and surmounted bya broad, mushroom - shaped cap. The interior is painted a dead black, and as an additional precaution against the entrance of light it carries a sleeve of the form shown in fig. 131. This effectu- ally cu
. Carnegie Institution of Washington publication. VENTILATION OF DARK-ROOM. 149 LOADING SHELF 2 ft. 3 in. 5! DOOR I Fig. 135.* in use much of the time, some The writer accomplishes this by an electric fan placed in the mouth of an air-shaft which extends from the ceiling to 6 or 8 feet above the roof. These shafts are cylindrical, i foot in diameter, made of heavy sheet- iron and surmounted bya broad, mushroom - shaped cap. The interior is painted a dead black, and as an additional precaution against the entrance of light it carries a sleeve of the form shown in fig. 131. This effectu- ally cuts out light. The air is pumped out so rapidly by a de- vice of this sort that not the least inconvenience is experi- enced in working all day in a very small room. If only one or two persons The very convenient heavy camera shown in fig. 124 may also be used for natural-size work, arranged as shown in fig. 129. In this connection the Starrett cross-level shown in fig. 130 will be found very convenient for leveling the back of the camera. Very excellent cameras are made by the Century Camera Company. Their Long-focus Century Grand leaves little to be desired in the way of a convenient, perfect-working in- strument. The dark-room for development is an important subject. The chamber must be light-tight. At the same time it ought to be roomy and well ventilated. If the room is small and means of removing the foul air becomes Fig. *Fic. 135.—Diagram of small dark-room shown in fig. I3J. Standing in the middle, a man can touch the walls in either direction. In the ceiling is a foot-wide pipe extending 6 feet beyond the roof and capped with a broad mushroom top. In the lower end of this pipe is an electric fan, which pumps foul air out of the room. Light is prevented from entering by partial cross-septa projecting from opposite sides of the air-shaft, and also by blacking its inner surface. fFic. 136.—Wall case for preserving from dust and scratches the enamele
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