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376 RICHARDSON'S BLUEBOOK OF PROJECTION
screen illumination obtained with the high intensity direct current arcs using rotating positive carbons and operating at arc currents ranging from 65 to 150 amperes.
(101) This gap not only manifested itself by a wide difference in current consumption, but also in screen illumination. (102) The color of the light from the low intensity mirror arc installations, while appearing a brilliant white when viewed by itself, is actually a yellowish white when compared with light from the high intensity sources.
(103) A careful study of carbon consumption by theatres in this country and Canada showed that approximately 60 per cent of the total fell into the field of low intensity mirror arc operation, and comprised a large percentage of the smaller theatres.
Briefly stated, the above are facts upon which was based research work that has made available to small theatres new light sources providing the same blue-white light that characterizes the screens of the larger theatres, and at sufficiently low expense of operation to impose no extra heavy burden.
(104) This marks a real forward step in projection. It not only raises the standard of screen illumination in the smaller theatres, but also provides a greater comfort of vision to theatre patrons. These new light sources are well worth consideration by exhibitors and projectionists in all small theatres.
(105) Two types of carbons have been designed for these new lig'ht sources. First, there is the new, high intensity, copper coated carbon for the alternating current high intensity light source. Second, there is the new, copper coated carbon for direct current, highintensity, non-rotating, positive light source, popularly known as "Suprex."
The New A.C. High Intensity Arc
(106) This light source is quite different in character from any previously placed before projectionists. It is essentially a development having its base in the ordinary