612 ANNUAL REPORT SMITHSONIAN INSTITUTION, 1914. 
THE MATERIALS OF ILLUMINATION. 
The materials of ilumination may be classified as illuminants— 
natural and artificial—lighting auxiliaries, and fixtures (fig. 2). 
Considering first incandescent electric lamps,’ it may be noted that 
increases in the efficiency of light production have been accompanied 
by increase in the variety of illuminants both as to types and sizes. 
Neglecting for the 
moment other qual- 
ities than the 
efficiency of light 
production, your at- 
tention is directed 
to the diagram in 
figure 3. This 
shows improvements in incandescent electric lamps which were made 
available some years ago and the status of lamps of more recent 
development. It will be noted that the advances in the efficiency of 
light production have been marked. The carbon filament lamp 
which had remained without material efficiency improvement from 
1893 to 1905 was at that time improved through the development of 
MATERIALS OF ILLUMINATION 
ILLUMINANTS 
NATURAL | ARTIFICAL 
FIXTURES 
AUXILIARIES 
Fig. 2. 
LUMENS PER WATT. 
“MAZDA DRAWN WIRE 
NERNST 220¥,AC.+ 
T 
+ TREATED CARBON 
the so-called ‘‘metallized”’ carbon filament, and in that form remains 
the most efficient type of carbon filament incandescent lamp. The 
carbon filament lamp had been the standard form for general electric 
lighting, and continued to be the standard lamp and the most largely 
produced lamp until about 1912. Its preeminence was challenged 
before that time because of the adoption of the metallized carbon 
1 Incandescent lamps: ‘A new carbon filament,’’ Howell; Trans. A. I. E. E., 1905, p. 839. “New types 
ofincandescent lamps,’’ Sharp; Trans. A. I. E. E., 1906, p. 815. ‘‘ High efficiency lamps,” Doane; Proceed- 
ings N. E.L. A., 1910. “Recent progress in the art of lamp making,” Randall; N. E. L. A., 1913. “Tung- 
sten lamps of high efficiency,” Langmuir and Orange; Trans. A. I, E. E., 1913, p. 1915, 
