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MANAGERS AND PROJECTIONISTS 627
The Power's Projector
THE Power's projector may be had in several models, the latest being the six-B, with Type E lamphouse.
Figs. 231 and 232 supply dimensional data which will be of value in planning the projection room.
Type E lamphouse is illustrated in Fig. 233. It is 11.5 inches wide, 18 inches front to back and 22 inches from floor to roof. The doors are well braced and double walled, with a half-inch air space between the two walls through which air circulates. The metal used is heavy Russian iron.
The top is so arranged that it may be connected with a pipe leading to the open air or to the projection room vent pipe. f In the right hand door is a pin-hole projector with a ground glass screen, held out two inches by a metal casing, upon which screen an image of the crater is projected. Upon this screen lines either are, or may be scratched to represent the proper 55 degree angle position of the crater. The other door has an ordinary observation hole covered by 6 colored glass.
In the right hand back corner is a small incandescent lamp so arranged that it lights when lamphouse door is opened.
The condenser mount is illustrated in Fig. 234. The lenses are carried in a metal holder which is calculated to equalize the expansion of the thin edge and thick center of the lens, and thus reduce breakage. The lamp rack-bars are threequarters of an inch square. The bearing through which they slide is 2% inches long. The surfaces which grip the carbons are 1^4 inches long, of cast iron, dull nickeled. The carbon clamp screws are 5/16 inch in diameter; the leverage for clamping the carbons is ample.
USE GRAPHITE.— The carbon clamp screws and other working parts of the lamp must be kept lubricated with powdered graphite. A dry, unlubricated carbon clamp screw is an abomination and a nuisance. The construction of the lamp, as a whole, is rigid and good. On the front oi the bearing carrying the rack bars is a heat shield of asbestos. The lamp has all the necessary, usual adjustments. The dowser is inside. It has two handles so that it may be operated from either side of the projector. These handles