DEVELOPMEN'S IN ILLUMINATION—MILLAR. 619 
The study of auxiliaries from the several viewpoints of light dis- 
tribution, light absorption, color modification, dust depreciation, etc., 
has been an important part of recent developments in the field of 
illumination. The light distribution curve has become a familiar 
part of manufacturers’ data and has been influential in emphasizing 
the importance of correct design and low light absorbing qualities for 
reflectors and globes. It has been shown that there have been 
marked improvements in the design of lighting auxiliaries. Like- 
wise, there has been a notable growth in the knowledge of the use of 
such devices and in the discriminating selection of the best available 
for given purposes. 
The literature of the art is rich in discussions of the physics! of 
light production, optical principles, color, etc. Knowledge of these 
subjects has been distributed rather rapidly through numerous pres- 
entations before organizations of men interested in lighting 
In the measurement of light, notable progress has been made in 
recent years. The measurement of total flux and light distribution 
in the laboratory and the measurement of illumination intensity and 
brightness in lighting installations has been developed and now 
forms a standard part of illuminating engineering practice. 
Beyond the introduction of certain refinements which have pro- 
moted accuracy of results, there have been no important develop- 
ments in the practice of commercial photometry during recent years. 
Probably the most important development in this field has been the 
reduction in the size of photometers, which has resulted in making 
portable photometers available for the study of illumination. A 
recent broadening of the scope of such study has included the meas- 
urement of brightness as an important branch of photometry.? 
A number of investigators are engaged in the study of the problem 
of photometry by nonocular means. The thermopile and the photo- 
electric cell, with possibly some alternatives, are looked to for assist- 
ance, in the future. While nothing of commercial practicability has 
yet demonstrated its value, progress is being made. 
The variety of color values of the several important iluminants, 
and the other color values which for scientific purposes must be 
measured, create a requirement for standards of light of several 
1 Physics and chemistry: ‘‘ Transformation of electric power into light;’’? Steinmetz; Trans. A. I. E.E., 
1906, p. 789. ‘‘Color values of artificial lamps;’’ Stickney; Trans, Illg. Eng. Soc., 1907, p. 282. ‘‘The 
theory of flame and incandescent mantle luminosity;’? Fulweiler; Trans. Illg. Eng. Soc., 1909, p. 635. 
“Luminous efficiency;”’ Trans. Illg. Eng. Soc., 1910, p. 113. ‘Some chemistry of light;’”? Whitney; Gen- 
eral Elec. Review, 1910, p. 101. 
2 Photometry: *‘The integrating photometer;’’? Matthews; Trans. A. I. E. E., 1902, p. 39.- “‘Tlumina- 
tion photometers and their use;’’ Millar; Trans. Illg. Eng. Soc., 1907, p. 548. ‘‘A new universal photom- 
eter;’? Sharp and Millar; Elec. World, 1908, p.181. ‘‘The integrating sphere in industrial photometry;” 
Sharp and Millar; Trans. Illg. Eng. Soc., 1908, p. 502. ‘‘Color measurements ofilluminants;” Ives; Trans. 
Illg. Eng. Soc., 1910, p. 189. ‘Illumination tests; Sharp and Millar; Trans. Ilg. Eng. Soc., 1910, p. 391. 
“‘Photometry of large light sources;’’ Stickney and Rose; Trans. Illg. Eng. Soc.,1911, p.641. ‘‘Photom- 
etry at very low intensities;’’ Bell; Trans. Illg. Eng. Soc., 1911, p. 671, 
