618 ANNUAL REPORT SMITHSONIAN INSTITUTION, 1914. 
are more largely used, have been improved somewhat with the 
improvement in taste in regard to design which is gradually being 
wrought among the public at large. At least, it may be said, that 
the atrocious fixtures which were placed in moderate priced houses 
20 years or so ago are now supplanted by more tasteful fixtures. 
Plate 2, figure 1, shows a cluster of electric lamps which is typical 
of those sold 10 years ago. Contrast them with the view in plate 2, 
figure 2, of modern fixtures designed for the same class of use. The 
latter are superior in almost every respect and, while possibly more 
costly, yield a much better service return upon, the investment. 
It is thus apparent that progress in recent years in the design 
and construction of materials of illumination has been rapid, and 
that the report of recent developments must be considered to be 
encouraging in so far as the materials of illumination are concerned. 
THE SCIENCE OF ILLUMINATION. 
The science of illumination may be considered to comprehend 
engineering, vision, and esthetics. 
Principles of engineering—Considering first the principles of engi- 
neering in so far as they form a part of the sctence of illumination, it 
may be said that the subject of 
supply falls properly under the 
headings of electrical or gas engi- 
neering. The lighting practitioner 
must have a working knowledge 
of usual systems of supply, but no 
special knowledge is essential. 
In the matter of installation! the practitioner needs to be some- 
what more skilled. The electrical contractor, plumber, etc., are 
prepared to handle installations effectively, but are in need of 
guidance of the illuminating expert; hence, the latter requires a good 
working knowledge of the subject. 
A thorough knowledge of the design, construction, lighting quali- 
ties, and operating characteristics of artificial iuminants is essential, 
and this subject has not been neglected in the literature of the art. 
Daylight? also has been studied as to direction, diffusion, intensity, 
color, etc. Very complete information regarding sources of illumina- 
‘tion is thus available to the practitioner. 
SCIENCE OF ILLUMINATION 
Fia. 6. 
1 Operating characteristics of illuminants: “Deterioration of gas lighting units in service;”’ Pierce; 
Trans. Illg. Eng. Soc., 1912, p.677. ‘‘ The relation of the incandescent lamp to the lighting service; ’”? Cooper 
and Campbell; National Elec. Light Assn., 1913, p.400. ‘‘The proper lamp for a circuit;’’ Campbell and 
Cooper; N. E. L. A., 1912, vol. 3, p. 338. 
2 Daylight: ‘‘ Daylight illumination;” Marsh; Trans. Illg. Eng. Soc., 1908, p. 224. ‘‘The intensity of 
natural illumination throughout the day;”? Lewinson; Trans. Illg. Eng. Soc., 1908, p. 482. ‘‘ The distri- 
bution of luminosity in nature; ” Trans, Illg, Eng. Soc., 1911, p.687. ‘‘Daylight;’’ Nichols; Journal of the 
Franklin Institute, 1912, p. 315. 
