We use Optical Character Recognition (OCR) during our scanning and processing workflow to make the content of each page searchable. You can view the automatically generated text below as well as copy and paste individual pieces of text to quote in your own work.
Text recognition is never 100% accurate. Many parts of the scanned page may not be reflected in the OCR text output, including: images, page layout, certain fonts or handwriting.
92 MAGIC LANTERN WITH NERNST LIGHT [Cn. Ill
§^139. Management of an exhibition with the Mazda lamp.—
The exhibition should be managed as for the arc light (§ 26-41).
One must remember that with this relatively weak light only a small screen image should be attempted, and that the room must be relatively darker than for the arc light. In brilliancy the screen images will be more like that of the old lanternists with their weak lights. Clear lantern slides are especially desirable. The very opaque lantern slides sometimes met with can only be well shown by a large arc lamp.
MAGIC LANTERN WITH A NERNST AUTOMATIC LAMP
§ 140. This is also an excellent lamp to use with a magic lantern in a small room. Some forms are automatic in starting when the current is turned on, and some have to be specially heated. The automatic form is to be preferred, for it is no more trouble to run than an ordinary incandescent lamp. It takes some time, usually one to three minutes, for the glowers to come to full brilliancy after the current is turned on. They are made for the lantern with one, two, three and four filaments or glowers. The single glower approximates most closely to the arc lamp in the smallness of the source of light. Of course, with the multiple glower lamps a greater amount of light is given off, but they make an extended source. Whether the lamp has one or more filaments it can be attached directly to the house lighting system through any incandescent bulb socket as described for the Mazda lamp (§ 137).
§ 141. Rheostat or ballast for the Nernst lamp. — This lamp like the arc lamp is always used with a balancing device, but unlike the arc lam]), the ballast is an integral part of the lamp as purchased, and not a separate apparatus as with the arc light (fig. 54, 55 and i).
The glowers and the ballast must be adapted to each other and both must be adapted to the line voltage.
The ballasts, which are enclosed in a vacuum glass, as with an incandescent bulb, sometimes burn out. The filaments will not then glow when the current is turned on. If a ballast burns out it must be replaced by a perfect one.