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So MAGIC LANTERN WITH SMALL CURRENTS [Cn. Ill
§ 124. Room for projection. — Any room may be used at night, and this makes these magic lanterns especially adapted for the home.
In the daytime, of course, the room where they are used must have shutters or curtains so that it can be darkened.
§ 125. Screen for the image. — The screen need not be over three or four meters square (9-1 2 feet) . For many purposes a large sheet of cardboard, 72x120 cm. (28x44 in-) makes the best possible screen (see Ch. XII).
For home use a white wall or a well stretched sheet will serve. If the screen is to be used frequently in the same place in the laboratory or home it is desirable to use a white wall or a regularly painted screen (see § 621-630).
§ 126. The magic lantern and its support. — Any of the good modern forms of magic lantern can be used. Special small and compact lanterns have been constructed for this purpose, and they are excellent and cheap (see prices in the appendix) (fig. 51-52).
For a lantern support any table of sufficient height may be used. A pile of books or an empty box on an ordinary table will serve to raise the lantern sufficiently.
ARC LAMPS FOR THE HOUSE CIRCUIT
§ 127. Small arc lamps, using small carbons only, are convenient ; but the ordinary large arc lamp can be used if the screws for clamping the carbons are long enough, or by means of bushings or adapters for the small carbons (for wiring and rheostat, see § 128-129).
The small carbon arc lamps are easily managed, and the amount of light they give (see § 756) much more than offsets the attention they require over the other lamps used on the house circuit.
If a lamp must be purchased for use on the house circuit, one of small size is preferable. They arc designed for the small carbons only. They arc nearly always of the hand-feed type, but when direct current is available there arc automatic lamps to be had. The Thompson automatic arc lamp, and the Bausch & Lomb