614 ANNUAL REPORT SMITHSONIAN INSTITUTION, 1914. 
Paralleling the improvement in efficiency of light production by 
means of incandescent lamps have come improvements in larger elec- 
tric iluminants.'| The pure carbon open are lamp was supplemented 
in about 1893 by the inclosed carbon lamp, which largely sup- 
planted it in spite of a lower efficiency because of more desirable 
operating characteristics. This inclosed carbon are lamp has been 
for a number of years the standard street lighting illuminant of 
America, and only within the past two or three years has yielded its 
position of preeminence in that field to the newer and superior forms 
of arc lamps. The intensified carbon are lamp has found consider- 
able application in the lighting of interiors, principally stores. In 
this lamp pure carbons of relatively small diameter are operated at 
high current density within a globe which partially restricts the air 
supply. The resultant light is more nearly white than that usually 
obtained from the carbon are lamp and offers some advantages for 
store hghting purposes. 
The metallic electrode are lamp, of which the magnetite and me- 
tallic flame lamps are the principal examples, has come into large 
use in street lighting and more than any other type of lamp has 
supplanted the inclosed carbon are lamp. This lamp differs radi- 
cally from earlier forms of are lamps in that the light is produced 
by luminescence and emanates wholly from the are stream, whereas 
in the several forms of pure carbon arc lamps the light is produced 
by incandescence of the electrode ends. 
The flame are lamp (short-life form) is the highest achievement 
in efficiency of light production among commercial electric illumi- 
nants. In its earlier forms ,it suffered from short electrode life, 
which made its operation costly and practically limited its usefulness 
in this country to display lighting. In repetition of the history of 
the pure carbon are lamp, the flame are lamp, which is equipped 
with carbons impregnated with various salts, has been adapted to 
secure long electrode life by partially inclosing the arc and employ- 
ing large diameter electrodes. As in the earlier lamp, this operating 
advantage has been secured at the expense of loss in efficiency, and 
the long-burning flame are lamp is not to be confused with the more 
efficient short-life flame are lamp in this respect. 
The gas-filled Mazda lamp,? small sizes of which have been in- 
cluded in consideration of incandescent lamps, has not yet emerged 
1 Are lamps: “The invention of the inclosed are lamp,’’ Marks, The Sibley Journal of Engineering, 
October, 1907. ‘‘ Properties and industrial applications of the flame are lamp,”’ Blondel, International 
Electrical Congress, 1904, vol. 2, p. 729. “The electric arc,” Steinmetz, International Electrical Congress 
vol. 2, p. 710. ‘‘The metallic flame arc lamp,”’ Stephens, Trans. Illg. Eng. Soc., 1907, p. 657. “ Design 
of luminous are lamps,’”’ Halvorson, General Elec. Review, 1911, p. 578. “Are lighting,’”’ Steinmetz, 
General Elec. Review, 1911, p. 568. ‘‘ Ornamental luminous arc lighting at New Haven,’’ Halvorson, 
General Elec. Review, 1912, p. 220. ‘Inclosed flame arc lamp,’’ Chamberlain, General Elec. Review, 
1912, p. 706. 
2 Mazda gas-filled lamps: “‘ Tungsten lamps of high frequency,’’ Langmuir and Orange, Trans. A. I. 
E. E., 1913, p. 1915. 
