article on this subject is Die Lösung der Heizfrage bei Gemäldegalerien und ähnlichen Sammlungsgebäuden, by R. Stegemann, Museumskunde X, page 133.
We have not yet thoroughly come to understand, either, the importance of proper ventilation in the museum. Ventilation does not mean merely provision for a change of air. It means that no air should be taken into the museum that has not been screened and washed. Any one who doubts the amount of dust that is brought in by air can be easily convinced by once being taken to the intake in some building where the air is properly sifted. The system most commonly in vogue is that of drawing the air through cheese-cloth screens. Large wooden frames are provided, over which bags made of cheese-cloth are passed. These bags are scraped one day and changed the next. The amount of dirt which has accumulated on both sides of the bag is so great that it seems incredible. Another system is that of using exceedingly fine copper-wire screens over which water pours continually. The air passes through this screen and the water washes off the dirt which accumulates. At the same time the air is supposed to receive some dampness. This system is thoroughly satisfactory in summer, and if the air is not damp enough already; in winter, how-
