DEVELOPMENTS IN ILLUMINATION—MILLAR. 615 
from the developmental stage, but is known to be among the very 
highest efficiency electric illuminants, especially in its larger sizes. 
The mercury arc lamp is available in two types. The low-pressure 
are in glass tubes is the earlier form and is in more general use than 
the high-pressure quartz tube lamp. The latter, however, surpasses 
it in efficiency.* 
The Moore tube, filled with nitrogen for general illumination pur- 
poses, has been used to a limited extent for special classes of light- 
ing. Smaller sizes in which carbon dioxide replaces nitrogen are 
used only as artificial daylight. 
The Neon tube, as devised by Claude of France, marks a distinct 
advance in the efficiency of tube lighting. Whereas the Moore 
CHRONOLOGICAL DIAGRAM OF LARGE ELECTRIC LAMPS. palmer ee 
50 
E 
c 
4 
: 
2 
A FLAME ARC — YELLOW 
= 
[2% 
a 
+ MAZDA-GAS FILLED—- LARGE 
2 MERCURY VAPOR— QUARTZ (220V,D.C) +} 
[+772-10 AMP LONG BURNING - FLAME ARC— WHITE 
aoe + MOORE TUBE + 
CARBON ARC NITROGEN 
830 2 4 e@ = 60 2 4 Se fay lo t a4 
Fig. 4. 
nitrogen-filled tube yields light of a pinkish-yellow tinge, the Neon 
tube gives light which is red.? 
The diagram, figure 4, summfarizes and compares the light-pro- 
ducing efficiency of these several large illuminants. The inclosed 
carbon arc lamps and the Moore tube are the lowest in efficiency. 
The 4-ampere magnetite lamp is of substantially the same efficiency 
as the old open carbon arc lamp. The 6.6-ampere magnetite and 
the low-pressure mercury vapor lamp are next in order, just failing 
to reach the efficiency of the long-burning flame are lamp, of the 
quartz high-pressure mercury vapor lamp, and the Mazda gas-filled 
lamp. <A short-burning flame arc lamp producing 36 lumens per 
watt is distinctly the most efficient of these large illuminants. 
1 Mercury vapor lamps: “ Notes on the Cooper-Hewitt lamp,’’ Cooper-Hewitt, Elec. World and En- 
gineer, 1910, p. 679. ; 
2 Tube lighting: “‘ Light from gaseous conductors within glass tubes,’’ Moore, Trans. A. I. E. E., 1907, 
p. 605, ‘‘Neon tube lighting,’’ Claude, Trans. Ilg. Eng. Soc., 1913, p. 371. 
